Thanks for the update Dan.
I tried editing the pdf on a local folder, and updating via resource manager worked now just fine, when .afpub file was also in the same local folder.
As a notion, when using GDrive, my pdf and .afpub files are usually located in different folders/locations, since I have a lot of organized files to work with. Having said this, I tried to move the files into the same folder in GDrive to see if that would be the cause. Unfortunately that did not resolve the issue and Publisher froze again (program not responding). I waited 7 minutes before forcing the program to quit, I took a timer
The changes I've made in GDrive have been quite minor: editing text, moving an image, adding a vector line on a map, etc.
edit: I've usually worked with a workaround by pressing "Replace document" -button in the upper panel. With that way, the pdf-files update just fine even in GDrive. So it's the resource manager that seems to cause the issue for me. This workaround is fine for me, but with many pages or spreads of pdf, updating them one by one is a bit tedious.