Soft spots on floor (gypcrete)

[Chris Herrera]

Under contract on a 4plex and the last issue I still haven't figured out is some flooring issues. 

I've noticed a couple parts in 2 units the floor sort of gives in and you can feel the floor sink in a bit

The inspector said the foundation was fine, but wasn't too sure what the issue was. He later said the concrete mix (gypcrete) under the flooring might have just cracked and given in.

Anybody have experience with gypcrete and if that's a valid issue?