(I also copied this reply to your other message in the 1.14 release notes)
Hi Onno_199!
You don't need to purchase the game again, it should be in your library. Click on the dropdown arrow next to your username in the upper-right corner, and go to library. It should be available to download there. We've released a few updates which were meant to help some of the graphics issues reported, so I suggest trying the latest version and seeing if the issue persists.
If you are on the latest build and it is still causing issues, sending us a log file could help us track down the issue here are some instructions: https://idolsofash.com/support.html