Composition window doesn't show content (except when deleting the settings.txt)

Dear Community,

I updated to the latest After Effects CC 2018.3 (on Win 10) and my composition window would not display a composition anymore. It is not blank though, like in many other cases I've seen described here. Instead the initial comp window remains almost unchanged with the two options of either "new composition" or ""new composition from Footage" (mabye my translation is a bit off, I use the German version). The options are not interactive after opening a project but static - like a frozen screen, everything else seems to work as usual.

After having tried almost everything that has been recommended in similar issue-reportings and not having found an answer that fixes my problem, I give up and came here for your help.

I found one thing, that fixes the problem at least temporarily. If I go to AppData\Roaming\Adobe\After Effects\15.1 and delete the "Adobe After Effects 15.1 Settings.txt" (in may case "Adobe After Effects 15.1 Einstellungen.txt") my composition will show again upon restart (provided AE was closed properly via Task manager - and doesn't run in the background anymore).

Unfortunately - this process needs to be repeated each time I start AE and also - I like to have the option to safe my settings again.

I made a little observation along the way, which might be a clue (or not). Weirdly - every other time it seems to work even without me deleting the txt file, yet the next time again the same problem. So I checked and the settings.txt is always different in size. AE seems to overwrite the file. If the text in the file is short AE will show the Composition window content. If it is long with many details - it won't. I suppose the devil lies there. I don't know what to do with this - which setting might be the problem? If it helps - here is a weTransfer Link to the two txt files to compare.

What can I do? I am on a tight deadline - I would appreciate help SO much!

I have tried so far:

- Updating the drivers of my nvidia GeForce GTX 1060 6GB

- "Fit to screen" is on - hence not a zoom problem

- I tried setting the AE cache path to the SSD and then the HDD

- Disk Cache is set to 46 GB and emptied

- I tested to run AE as admin user

- I deleted and reinstalled AE

- Tried both CUDA and "Mercury Playback Engine Software Only"

- and a lot more I cannot recall

- Also: Ctrl+Alt+Shift for resetting the preferences while AE opens - does not seem to work. There is no dialog or anything else responding to it.

My settings:

- Intel Core i7-6700K

- 500 GB SSD Samsung EVO 850

- 1 TB HDD

- 16 GB RAM (which in my settings AE can use up to 13 GB)

- Win 10 Pro 64 Bit (latest)

- nvidia GeForce GTX 1060 6GB (as also recommended by Adobe