Imported collection not retained between app restarts (working locally)

I have found a few discussion regarding collections not being preserved between restarts, but usually they revolve around logging in to Postman account. In our case our users do not use Postman accounts and use Postman as locally only. We are able to create new collections and they are preserved between Postman restarts. But if we try to import a collection, it disappears next time we start Postman. Same happens if i create a new collection, export it, delete, restart Postman, import it and restart Postman again.

Just updated to 9.6.1 a few weeks ago. It was a very old 7.x version before and was working as expected. I think it was still working like that in some 8.x versions. Maybe something has changed in 9.x and now account (workspace) is mandatory to save imported collections?

If so, which older version still allowed to save imported collections between restarts when working locally? And is there a download? We still have installers for older version, but don’t want to install ancient versions that might have vulnerabilities or incompatibilities with new code, etc.