thl 4000 can't install apps - insufficient storage On my thl 4000 I can't install apps - I get 'insufficient storage' massage, but I have 168M of free storage and the apps are 2 - 8 M

I tried to follow all the instructions on the different forums, it helped at first but now nothing works.

android v - 4.4.2
I found the following work around - go to 'play store' 'app info' and do - 'Uninstall updates'.
This works but 
finally I end up resetting my phone to factory setting - and the message doesn't appear any more and also I have lot's of free storage.