Print Mode freezes Dorico

it happens quite regulary that Print Mode freezes my Dorico project:
I open my project
I setup a new score layout.
I work and tweak this layout in Engrave Mode
The last Save I do is at 08:07
At 08:50 I switch to Print Mode to do a .pdf export
I usually change the page size from US Letter to DINA4
Dorico has to recalculate…
At this point the application freezes - or better stalls.
I try to do a Save and Save as - both without function
The original file still shows 08:07 as last time saved
I look into my Dorico Backup Folder - last saved file 08:07…
This does not help…
I have to force quit Dorico - and the work of this morning will be lost probably…
After force quitting Dorico I start the application again - and luckily I can recover the project, even if I did not find it in the Backup Folder. I check my Preferences, Dorico is set to do a backup every 5 minutes. This does not seem to be working.
I must be missing something (the difference between Backup and Autosave).
Where can I find the Autosave files?
And why can I not set Doricos’ Preferences to use DINA4 as default?
Thank you for help.
This is the Diagnostic report - after reopening the application:
Dorico (2.8 MB)

On the print/export/page size question, we’ve done this before: another try on DIN A4 default paper size
If you’re exporting a Normal job as PDF, there is still no point changing the paper size in Print mode.

And for Autosave vs backup, yes, you’re muddling them up. AutoSave files are stored in ~/Library/Application Support/Steinberg/Dorico 3.5/AutoSave until the project is closed normally, at which point they’re moved to the Trash. Backup files are stored wherever you tell Dorico to store them, and are generated each time you manually Save/Save As.

Thank you pianoleo for explaining the Autosave.
Concerning the changing to DINA4:
yes I know, this step is not essentially necessary when exporting to pdf.
If I would instead want to Print, I do would have to change to papersize to DINA4 though. The freeze happens after performing this step, not when trying to export. It would be good, if Dorico could register my personal/regional/international preference (Papersize DINA4) right at the beginning. Then it would not need to recalculate at a later point.
For me this is a daily issue which I have not been able to solve yet.

Just in case it is the same issue: I had another Dorico stall today - after trying to add players to a new flow. Dorico still seems responsive - but does not do anything - so I have to force quit.
I will attache the Diagnostic report and a video to show, what had been going on:

Dorico (2.7 MB)