Cache: trying to remove non empty directory

Please look at the Tracy output first: http://www.jakubmisek.cz/tracy.htm

This happens occasionally for example twice a day when I try to reload the page, submit the form,…
When I look into this directory, it's empty and after repeated reloading the page it works fine
I think it began maybe week ago, I am not sure if it has something to do with Nette update (the newest 2.2.x version), but it's really weird. I looked at the function and this error message doesn't make sense to me.

This website is in development now so I test it mainly on local server. I haven't noticed it on production server yet but of course the reason could be very simple – we don't use it there so much now..

I found similar reported problem a few years ago: https://forum.nette.org/…konstruktoru