Exporting a motion graphics template sometimes fails with a missing files error (this is bug 1). This basically cancels the export, but has an even worse side effect (bug 2):
As I understand mogrt files are aftereffects projects collected and compressed into a zip file. The zip file only contains the assets that are needed for the composition exported as a mogrt. I'll call this project the "partial project", since it contains only a fraction of the original.
To achieve this, while exporting, after effects silently closes the current project in the background and opens this small partial project in place of it.
If there is an error while opening this partial project, the export process terminates, however after effects does not restore the current original project, but leaves the partial project open, BUT still references the original project file as the source. Your original composition will be opened as if nothing happened, so you may not notice, that there is problem. So if you save your project in this state, you will overwrite your original project file with the broken partial temporary project that was intended for the mogrt export, which essentially destroys your original project. And there is no recovery after that point, only your autosave folder.

I have the latest version of AE 2020 (17.0.6) and I still have problems with playback which none were present in 2019. I push spacebar (or from the preview menu itself) to preview, it starts but then it wont´t stop, I have to force quit the program, this only happens with the Windows version, in MacOS it works fine, I just had to move my entire project to MacOS because otherwise I could not work. PLEASE fix this, after many updates of 2020 this bug/issue persists!
That's what happens when it plays the preview, sometimes it just won´t play no matter what, I have to close ÁE, open it and preview again and do that process all over again everytime it won´t even start the preview.

Only really recently has AE been crashing so bad it ends up being a hard reset on my system.

To preface, there is a good chance that my settings / set up / system could play a big part in what i'm experiencing, However just a few months ago on this same exact system and set up I did not have this issue. (maybe one in a blue moon). And I was working with fairly large 4k footage.

Quick summary of what just happened to me twice today (so far) and once yesterday. I'm doing general tasks in AE, with HD footage. (Nothing too big or too long - 20 seconds). The biggest difference from my normal workflow is i'm using mocha and Boris fx Silhouette.
I get the the Out of Memory error a lot more often. Even with purging memory, increasing maximum disk cache, and playing around with the RAM availble for AE. Its currently at 28gb with 4 for other applications.
I normally have it set at 20gb because i dont often exceed that usage.
After getting those error messages I click the error off 10 times (why does it have so many pop ups?) so I can save and purge memory. The big crashes have happened in AE, in the Mocha Plug in interface and in the Silhouette plug in interface.

The crashes resemble a powersurge. Monitors flashs, turn on and off and then wont turn back on till I unplug them and plug them back in. After that however, they turn on but do not connect to my computer until I am forced to hard reset my computer as I can't see my desktop anymore.

I've inspected my computer and surroundings to see if there is some sort of static discharge issue or if there is something wrong inside my computer and can't see anything out of place. But since this has happened 3 times in two days, doing the same task I need to assume is has something to do with After Effects. (Since I just started a new job I've been away from AE for a couple months and only started using it again this past weekend.)

Honestly I just wanted to rant for a bit, because I just started a new job working from home and need my computer and AE to function. These crashes have lost me hours of work, which doesnt give a good impression to my new position and have me concerned about my computer. I dont really expect anybody to specifically help me with anything, I just need someone at adobe to hear me.

I can post system specs and software specs if somebody wants to see. I really hope it would be a simple solution or user error, but I have tried many of the suggestions i've found online with no real impact.

Using aerender.exe to render a bunch of files I find that every randomth seldom time the log file output of aerender.exe (using -l logpath.log) will end abruply, without the last few lines that typically go:

PROGRESS: 18.11.2020 12:21:14: Starting composition “{{RENDER_ME}}”.

PROGRESS: Render Settings: Best Settings
..
PROGRESS: Time Span: Work Area
PROGRESS: Start: 0:00:08:04
PROGRESS: End: 0:00:11:12
PROGRESS: Duration: 0:00:03:09
..
PROGRESS: 0:00:11:11 (83): 0 Seconds
PROGRESS: 0:00:11:12 (84): 0 Seconds
PROGRESS: 18.11.2020 12:21:16: Finished composition “{{RENDER_ME}}”.

PROGRESS: Total Time Elapsed: 2 Seconds

Instead the render job apparently finishes, but the last few lines are not being logged, so it just ends with:

PROGRESS: 0:00:11:10 (82): 0 Seconds
PROGRESS: 0:00:11:11 (83): 0 Seconds
PROGRESS: 0:00:11:12 (84): 0 Seconds

I.e. there is no "total time elapsed" or "finished composition lines". It can happen on maybe 1 in 30 videos or so.

Applies to both AE2019 and AE2020.

I was using the last lines to detect when the rendering was done, but this causes it to just wait forever. Of course I could watch for the "Duration" and "End" lines, and then monitor the log until I see that the last frame has been rendered, but this seems more hacky than just getting the verification that it has ended.

I can't wait for the aerender.exe process to end with AE2020 because it just ends without waiting, unlike previous versions (AE2019 works fine).