Verrier.5870

Recently I have an issue, where my fps drops from around 50 to 18-20 for a few seconds, then goes back up to 50. This repeats pretty often, like every 5-10seconds. When I launch the game there are no issues for a good while -30min- and after that this keeps going until I restart the game. Then again for around 30min no issues and these fps drops start again. Anyone else had this/how could I fix it?I tried repairing the client, but it didn't fix anything.