Debugger error "Debug information is inconsistent"

Hi,

I am currently debugging a Scala program that runs smoothly. However when stopping at breakpoints, I do see all variables but not their values. Instead it says "foo = Debug information is inconsistent" in red. The "Evaluate Expression" feature returns "Cannot find local variable 'foo'".

I checked the the run configurations and nothing seems off. The code builds and executes normally. Just the debugger is confused.

I didn't come across any helpful clues on the internet. That's why I hope to get some general info how to fix this error here.

Cheers