Dry Brushes

[Pijus Balkaitis]

Hi I'm new to TVpaint.
time after time my brushes 'dry up', you can see in a picture.
no changes of settings fixes this, more experience colleagues can't explain what's happening.
only by re-installing TVpaint brushes becomes 'wet' again, but usually not for long.
any ideas where to begin? help would be appreciated!