'The application "DiskImageMounter.app" can't be opened.' - Sierra 10.12.2

What I have seen of this is an inability of 10.12.2 Finder to open sparsebundles on the Time Capsule or on another drive connected through it. I see Time Machine backing up to to my Time Capsules just fine. I also find that the files it is creating ARE still able to be opened from Finder from a 10.11.6 El Capitan system that also can access the Time Capsules. The files and backups into them seem to be fine. Also Enter Time Machine seems to be working just fine and finding the backups as it should.

The problems I am seeing are just that I can not open sparsebundle files, including the ones made by Time machine, but also ones created by other means that are on a Time Capsule. Something is broken in 10.12.2 for Finder opening sparsebundle files on network drives (Time Capsule and perhaps other NAS type storage). I don't know if there are any other types of files giving trouble but there might be based on one or two postings I have seen elsewhere.

Are you seeing a problem other than in Finder trying to access Time Machine files on a Time Capsule? Can you describe what you are seeing?

I think your point about using Disk Utility is clear. Yes you can see the files using your approach.

My post I think you are replying to was to try to understand what the previous posted had asked about.

My issue in this starts with seeing that Finder access broken, apparently in the 10.12.2 release. I found the problem when I started to look into Time Machine deciding my Time Capsule backups had to be deleted and started over after doing some sort of verification. I tried to look at what was on the Time Capsule (using Finder as usual) and ran into the error and started investigating.

It seems clear 10.12.2 brought some sort of a bug in the underlying code. That needs to be fixed. But I am concerned that possibly there is more to it that could help explain the TM invalidation of existing backups which is something that would REALLY need to be addressed ASAP.

As a by the way, when I saw the error I called AppleCare. The third person I talked to bailed out of dealing with the error because I was reporting having seen it in connection with Time Machine backup files. He insisted looking at them with Finder was "unsupported" and that the only way that was supported was via Enter Time Machine. He would not address the error. Now that I have constructed a demonstration that does not involve files created by Time Machine I may try again. Maybe I will get someone this time who ill see there is a problem and do whatever they do to forward bug reports to the people who can deal with them.

Yes, I may even have heard something like that mentioned. And to some degree I can understand the Time Machine support people wanting to take the position to not support looking into the files that are made by Time Machine.

BUT, to disable it in a way that leads to an obscure error message like this would be entirely inappropriate, particularly if it was not announced, and if ApplleCare people don't know about it when you call about the error message as I did, and the ones I talked to did not know and were unable to find anything about it in their databases.

But, more to the point access to ALL sparsebundles on all network drives appears to be broken, not just ones created by Time Machine. They have much wider utility and are a well established capability. Disk Utility gives the means to create those files and they provide a considerably broader functionality than just Time Machine. You should be able to use them (at least for other than Time Machine), at least until and unless Apple decommits from them and announces it. I really doubt that is what is happening here. They have not disabled other aspects of sparse bundles or network access to them, and it would cause all kinds of problems if they did.

This really looks like an inadvertent bug rather than an intentional change. What I am most concerned about is how far the impact reaches - what else is impacted by whatever the problem actually is.

I have only been using Macs for about 28 years. Since at least OS X network all the Unix style stuff has been available to and used by many applications and developers.

I just want Apple to get on this one and fix it...

Yes, I have noticed this too. My test was even simpler. I put a simple .rtf text file on a USB thumb drive. When I plug the drive directly into my Sierra machine I can click on the file in Finder and it opens fine in TextEdit. When I plug the drive into the Time Capsule and do the same thing I get a similar error "The application "TextEdit.app" can't be opened. -36. If I open TextEdit I can find and open the file with no problem. All that is consistent with your observations.

When I do the exact same tests from my El Capitan system they work correctly. That is using the exact same Time Capsule on the exact same network. The only difference is the version of macOS/OS X.

It is clear that something is going on with 10.12.2 Finder accessing files on network drives such as ones implemented through a Time Capsule, and I think other NAS storage (.g. not just the internal drive in a Time Capsule).

I understand that network drives use different core file services from those used for direct connected drives. I seems clear something has changed in the Finder interface to the network file services (afp?). It seems when finder tries to acquire file info for a file you click on in it, and pass it on to an app that something has changed or been broken. What is not totally clear is if it is an actual bug or an intended change. (I mention that because of the statements I mentioned being made by AppleCare that make it conceivable that there was an actual attempt to stop users from messing around with Time Machine files by other than Enter Time Machine, and maybe they got it wrong).

I am interested in the idea of rolling back one point release. Have never tried to go back like that. What did you do?

Besides the particular problem we are discussion here I have been seeing another issue and I am wondering if whatever is going on with this one might somehow relate to that one. It is that periodically - like once a week or so I get an error from Time Machine saying it had run a validation on the Time Capsule backups and it has to start a new backup. As I understand it the Time Machine programs run those validations periodically more or less like the schedule I have been getting these problems and I am thinking there is some problem now with that validation process. I see the exact same problem with both the Time Capsules I have in use. Both of the Time Machines handle backups from both the Sierra and the El Capitan machines. The El Capitan machine does not have any problems, so it points to the possibility of Sierra related issues too.