I tried to update from 3.0.18.x to 3.0.19.8..
First time: I got the error "vmclasslanguage not found"
Second time: empty screen
Third time: OK
Beside this I will do further tests...
This is strange. I know that some others had also this error. I investigated it and noticed that the old vm installer used the "installed" files and not the new files for the update process. But I fixed this. I did some test update and I know also that others had no problems anylonger. So I wonder why you got it. Which installation method did you use?
I tried it again.
I restored a 3.0.18.7 backup
Then I installed 3.0.19.8 via Joomla installer.
This time I got a blank screen with the title: "Fehler: 0 Call to undefined method Vm:Table::checkTableExists()"
But refeshing the screen shows 3.0.19.8 as installed...
Then I tried another backup from a different site - same, same!
Then I tried a 3.0.18 backup. Same result!
Language problem (in my case German)?
PHP is 7.0.x