Missing Time Machine backups post Catalina Upgrade

For those of you following this thread, I wanted to link to a related thread re: "Time Machine gets stuck at end..."

https://discussions.apple.com/thread/250747673?answerId=251437770022#251437770022

I've extended my experence with this thread and asked a few clarifying questions. If you get a chance it may help to share yours as well. I've listed a few questions I thought might narrow the search, feel free to contribute.

Thank you for providing your experience, re: Apple and the Community, I think they occasionally scan them, but their primary way of interacting with issues is through their Bug Reporting site.

For my experience my backups just didn't show up when you enter Time Machine. I would only see backups kept locally on the computer which are typically just 48 hours back. However i have backup snapshots going back to May of 2019, which I'm hoping I don't lose

No issues with iPhone sync.

Initially I thought there was a background process simply updating the format of the backup files, after ~24 hours post initial upgrade I was again able to see my backups. However, this didn't last long. They all fell off and I was back to the last 48 hours. Since the yesterdays supplemental update I still do not have access to my full backup history.

I have a google alert for Catalina and Time Machine, I've noticed more activity around this topic over the past week, I suspect it will get more traction, be patient.

Update: Installed recent OS update released today (10/21) 10.15 (19A602). Once update completed all of the initial setup screens I had missed due to the forced restart during the "Setting up" phase were completed successfully.

Time Machine initiated large 5 gig backup of my system and left me with two TM Volumes.

iMac.backupbundle (was there before today's update) shows a current mod date and is a 'Package' volume of 1.32 TB. I have a 3.12 TB Fusion Drive and I have 2.43 TB available.

Prior to my Catalina upgrade I had access to snapshots going back to May 16th, 2019 on my Drobo 5N. A setup I've had running without issue; maybe 1 forced rebuild due to failed validation check a year on over the last 5 years I think I've had this setup.

I'm not exactly sure what types of logs or errors to pay attention to related to Time Machine, but when searching the Console i find few references to 'backup' or 'TimeMachine' in any recent logs.

I say recent because I did fine a 'TimeMachine' log but from some reason it hadn't been modified since 11/9/2018, which I haven't had a chance to look back to see if this date lines with any OS significant updates which might explain a discontinued log file.

cont.

Backups are running as expected, I only see snapshots going back to right after I installed today's OS update.   

I've provided a fairly in depth summary of my update challenges and setup context in my original post, but for quick reference, my Drobo 5n has a Time Machine configured volume of ~4 TBs available which is reported as 4.19 TB in the Time Machine panel I included above. 

 The drive is all green.

Since I don't have direct sight into the current capacity of the drobo "DeskBackup" volume, I have to estimate I have consumed 3.17 TB of the OS reported 4.19 TB.   I say OS reported because Drobo does things to dynamically allocate space based on RAID so I may have configured 4.5 or 4.0 Gb of space, but because of the way it manages this space it tells the OS what is can accommodate.  At leasts thats my RAID / Drobo / Beginners recollection of how it works. 

Based on what the OS is telling me I've consumed 76% of that volumes available space.  This is after the TM completed a large ~5.5 gb backup to the Drobo (NAS). 

Thanks for reading my thread, if I can expand on anything, lmk.  I'm genuinely curious about why this is happening. I hope what I've shared can be helpful to others. 

As a footnote; if you're also having issues with posting large replies or editing post let me know if you know what causes it. This is the second post I've had to split or duplicate because it wouldn't save the complete version.

Thank you Lurkums, can you provide a screenshot of the Service your NAS runs? I use a drobo, here is what I see that box broadcasting...

My iMac is backing up to the Drobo like normal, but continues to suppress backup snapshots going back to May 2019. No response from my bug report to Apple which is typical.

I've got google alerts on Drobo and Time Machine, I'm sure at some point someone is going to notice a group of users have lost direct access to Time Machine backup data as a result of the Catalina Upgrade.

Glad to hear I'm not the only one. I upgraded from 10.14, I didn't do I clean install. Lucky after 6 hours of work I was able to recover files from OneDrive that were deleted after the upgrade.

Note to one drive users, don't like iCloud sync the OneDrive folder, its a pain to clean up when it breaks. use ".nosync" on the root folder of the OneDrive sync folder to stop it.

Update: TM is now displaying my backups prior to my upgrade, I checked today and the TM interface displayed my complete backup history. I'm guessing there was a background process that kept those snapshots prior to my upgrade hidden. I now have access to snapshots going back to may 2019.

Issue appears resolved.

The only system change made was the removal and reinstall of OneDrives sync agent to resolve the issue that caused duplicate folders and file deletion. IDK if they are related.

It would be great if someone could clarify what is going on with TM backups.

Spoke too soon on my previous update yesterday. Received a TM notification this morning that my backup failed its last attempt. However, it completed its next attempt successfully.

As I was checking its setup and status I noticed the backups that were back yesterday are gone again. I'm back to only having access to local snapshots going back a few days.

There are now two TM files on my drobo TM share, iMac.backupbundle and iMac.purgeable. the backup bundle was last modified today at 11:11 am and was created May 2019. The purgeable file shows a mod date of May 16, the same date as the create date of the backup bundle.

The Backup file size is showing 1.3 TB, the share is configured to max of 4.19 TB. I can't see the size of the purgeable file.

I have not received any failed verification messages since upgrading to Catalina, I'm concerned about forcing one as it will wipe out my data prior to my upgrade to Catalina.