Catalina can't remember preferred wifi

The link is to two videos that demonstrate the behaviors that I have observed and which I believe are responsible for the problem that I have been facing, i.e. the list of preferred wifi networks is always empty and the computer never automatically connects to previously joined networks.

"AddPreferredNoGo.mov " shows me adding wifi's to the preferred list, OKing that and then returning to find the list empty again. I do this twice with one wifi first and then with 3 wifi's (I know this is not proper usage but it reads better). You can also see what happens to the "com.apple.airport.preferences.plist-new" file during these operations. The editor BBedit automatically shows any change in the file. After the added 3 wifi's, the fairly long addition to the file includes several SSiDs. Notice that they are exactly the same as the ones in the end of the original intact file which has just a single proper </plist> closure. It looks to me that the OS is actually not able to overwrite the existing contents of the file but still goes through the motions of doing so. When it thinks it has added something to the middle of the file it overruns the end of the file with the end of the original file.

"FilePeriodicallyCorrupted.mov" is a time-lapse recording of what happens to the "com.apple.airport.preferences.plist-new" file over time. The OS periodically tries to update the file and ends up only corrupting the end of the file. Notice the time stamp on the file in the folder list and how it changes during the video, indicating an attempt to modify the file. The display is in a BBedit window, and the editor seems to update its display of the file whenever it is changed by something else. The file is changed something like 6 times during the run of the video. I also went through the process of adding a wifi to the preferred list to show the change in the file.

Thanks Becaye and Old Toad for your attempts to help me. I did investigate your suggestions but they were not able to solve the problem. I decided to look into the guts of the OS files. My work experience is as an embedded systems programmer, so I have some knowledge of the nitty-gritty of computerized systems.

The enclosure above describes my investigations into the .plist files that have to do with wifi. Basically I found that the SystemConfiguration folder contains files with the extension ".plist-new" and the system is using those instead of the normal .plist files to handle almost everything wifi. The standard files in my folder have modified dates of 2015 or early 2016, which I think must be the last time they were useable. Whatever OS I started using then (probably Yosemite or El Capitan) must have found that the normal files were unusable and started the work-around of the .plist-new extension. My guess is that the original files became unusable possibly with some corruption of the permissions and they were not able to delete or change them (which I am unable to do, too) so they came up with the -new device. Then when they came out with Catalina, they neglected to give it the mechanisms to correctly handle handle the .plist-new files because most people didn't have any .plist-new files.

My wife is also running Catalina, and her folder contains only .plist files and works properly. I think the .plist-new files and the fact that the normal .plist files are not being used are the crux of the problems I am having. Most users are like her and don't have any problems, so it hasn't gotten fixed. I never had any problem with my previous OS (El Capitan or Sierra or briefly Mojave). Does anyone have connections with a MacOS developer who might be able to ask someone who works on that part of the code if any of this rings a bell?

Get info for the two types of file shows permissions that look exactly the same, yet I can move or delete or edit the .plist-new files but anything for the .plist files is forbidden to me. I take that to mean that there are hidden parts of the permission matrix, perhaps more than one level of "system". Have you ever heard anything like that? I AM able to move the copies I made of the .plist files. The difference probably is in the permissions of the folder for the system files. The readout of file permissions for the backup copies show me (instead of system), staff (instead of wheel), and everyone.

Anyway thanks again. Anyone else want to chime in?

I have added to the link snapshots from Time Machine for Nov 2015 and Feb 2016 when the SystemConfiguration folder changes from having only .plist files to including also .plist-new files. This period must be when the foundation to my problem was laid, but it did not appear until I "upgraded" to Catalina. My conclusion is that Catalina is the cause of the problem, although I briefly had Mojave installed and I possibly had the same problem with Mojave, and that is why I went on to Catalina. I just can not clearly remember. In any case, I operated successfully for a while with the .plist-new files. I don't believe I ever installed Sierra or High Sierra. I have been considering downgrading to one of those two because I lost use of one program important to me that will not run on Mojave or Catalina.

This timing seems to pin the cause of the .plist-new files to El Capitan, however I typically wait a year to upgrade to a new OS to let things settle down, so it might have been Yosemite that caused it. I believe I had both installed as some time (not the same time).

One other piece of information that might be pertinent: The computer involved was purchased used, I think from Ebay, at about late 2015. The model is early or mid 2015, so it was quite new. I will have to dig into my records to find anything precise. I don't remember what OS came with it or when I might have upgraded the OS. I might be able to dig some info about that from my records.

I hope all this additional information will allow someone the come up with a solution. At the moment I am thinking that downgrading to High Sierra would be the best option for me rather than moving on to Big Sur or the new one.

[Link Edited by Moderator]

The crux to this still unsolved puzzle is that the list of preferred Wi-Fis is always empty when I hit the advanced button on the Wi-Fi control page. This is true even after I have added one or more wifis manually and confirmed it. There must be a bug or something corrupted in the OS. I have not been able to find anything on the web that discusses this much less a solution. I need someone that knows a lot about the inner workings of the OS. I am getting close to going back to High Sierra. But I worry that whatever is broken won’t be fixed even with that. Help!

I have replaced the screenshot of SystemConfiguration for Feb 2016 with the one for June 2016. I mistakenly seized on the Feb one without close enough observation that it did not actually have any .plist-new files. The June snapshot is the correct first from TimeMachine that has .plist-new files.

Also I discovered FeedbackAssistant and submitted the problem to Apple with a link to this discussion.

There is a note that the link to the Dropbox files was edited by the moderator and it no longer appears with the text. I have not figured out how to access the links that are added from Link insertion icon at the bottom. Can someone enlighten me?