Pycharm 2017.2.4 inspections stopped working

HI all.

I just upgraded my pycharm to 2017.2.4 (ubuntu 16.04).  Something weird has happened to it. Basically, every error and warning it detects, remains there, even though I fix it.  There are also errors that are not errors, and they disappear at restart as well. 

For example, defining a global variable in the beginning of my program underlines the variable in red. When I write

Foo = 42

I get not one but two errors, possibly three depending on how fast I type. Foo is underlined in red, and when I hover the cursor over it, I get errors "Unresolved reference Fo" and "Unresolved reference Foo".  This is and was never an error but it is detected as such. If I create a real error, for example use something that is missing the import statement, this is of course detected as it should, but when I add the import, the statement remains red indicating an error until I restart. 

Basically, after ten minutes of coding my Pycharm window resembles a Christmas tree, as everything is shown as an error or warning. A restart fixes this, and ten minutes later I am again seeing a lot of red. 

This did not happen before 2017.2.4 upgrade. Could this be related? Or has something changed?  Or is it just me?