I’ve not been tracking this type of behaviour, but when I looked after your post, there does seem to have been a change. I used to be able to use Obsidian and another editor on the same file simultaneously. Not now.
When another editor has the file open, Obsidian no longer writes anything written in Obsidian to the file; it does, however, read immediately anything written in the other editor. So Obsidian is not completely frozen, just seems to have surrendered editing duties.
Yeah. Now looks very unsafe to use Obsidian at the same time as any other editor. But I’m not looking at consistency. Some editors seem to work fine - eg FocusWriter (but that doesn’t have autosave).
One of the problems is the same as syncing. The programs need to autoread the file and autosave frequently enough to keep up with what might be going on outside, and also play nicely with each other. I never used to have any concerns about this, but now I will check the detail before doing anything. Idk if there’s an operating system change behind it (I’m testing on W10).