Sounds like you have a kernel issue still if the issue persists with changing versions.
Not sure why you have 0 for the poll interval and 0m for the cache age.
How would I hunt down a kernel issue? Kinda lost over here to be honest.
All changes are made through the mount and it was working flawlessly before, so never changed it.
I know this is not a Ubuntu or Linux forum but is there a way to go back do the kernel I had before? Should never have changed it in the first place, I guess. Never change a running system… 
What version of the kernel are you running now? Are you able to tell what version you were running prior?
felix@gemini:~$ uname -a
Linux gemini 4.9.0-8-amd64 #1 SMP Debian 4.9.110-3+deb9u6 (2018-10-08) x86_64 GNU/Linux
My kernel version now is: Ubuntu 18.04.1 LTS 4.15.0-38-generic x86_64
And I was on: Ubuntu 18.04.1 LTS 4.15.0-33-generic x86_64
I just noticed that my debug log is full of stuff like this:
2018/10/30 14:10:21 DEBUG : : >Statfs: stat={Blocks:274877906944 Bfree:269409747800 Bavail:274877906944 Files:1000000000 Ffree:1000000000 Bsize:4096 Namelen:255 Frsize:4096}, err=
2018/10/30 14:10:22 DEBUG : : Statfs:
2018/10/30 14:10:22 DEBUG : : >Statfs: stat={Blocks:274877906944 Bfree:269409747800 Bavail:274877906944 Files:1000000000 Ffree:1000000000 Bsize:4096 Namelen:255 Frsize:4096}, err=
2018/10/30 14:10:23 DEBUG : : Statfs:
This is all over the log but tbh I don’t know if it was there before.
Thanks for your support mate!
Are you having a slow down or files missing? This thread was related to a slow down in speed. If your issue is different, I’d open a new thread and include some debug logs of the issue.
This has to be a kernel issue! I reverted to .33 and it is working flawlessly as before.
Do you know where this can be reported to the Ubuntu guys?