Ok, after some tracking of bugs on apache 2.4, it looks like it is its fault. Setting DirectoryIndex messes up webdav, fix in upper configuration is:
DirectoryIndex disabled
This is one of relevant bugs: https://bz.apache.org/bugzilla/show_bug.cgi?id=54914
Anyway this was fixed in apache 2.5 but got never merged into 2.4. It is a nasty bug that isnt very apparent, so it is quite possible that even 3rd party providers are not aware of it.
To the Enpass team: with more logging you would avoid so many "webdav doesnt work" messages, and your spam protection on this forum really sucks. Captchas are pain in the neck, while your spam protection is worse, I wasted hell of a lot of time to get those messages here.
And for god sake, implement already sftp sync, it is taking for years, if you have implemented piece of shit like webdav, sftp should be easier. You have bunch of 3rd party libraries on the internet, just use one.