Quit the store first
Shaders can only be cleared while the store and its games are closed.
What happened
Clearing shaders removes files that the store and its games read while they run, so Malbec does it only while they’re closed.
The fix
Click Quit the Store…, then clear shaders again. The first sessions afterwards can stutter while the shaders are built again.
When to write to us
If the store won’t quit, see The store is still running.
Email support@malbec.app. For a diagnostics file, choose Help › Export Diagnostics… in Malbec and attach the zip it saves. It has no account details, and your home folder is masked.