Well, I have removed files within datastore and cached files of js files several times and it didn't fixed the problem, but files actually has been recreating, so it wasn't issue of chmods or something. However - recreated js file root_library.js was just cut in some part, so it was impossible for all js stuff on site to work. Recreation of that file each time was cutted in different part. Changing memory limits and settings of php didn't solved the case. However I'm pretty sure that it was not a case when it was impossible to write files on server, which has been sugested in email response.
I'll soon update it on what you've asked now for so you'll be able to examine. Honestly, I don't want to make this problem happen again 😉