Quit your games first
Repairing the engine needs your games, Battle.net and Steam closed.
What happened
Repairing the engine replaces files that running games and stores use, so Malbec doesn’t do it while Battle.net, Steam or a game is open.
The fix
Click Quit Stores and Games…; Malbec asks before it quits anything. Then choose Repair Engine again.
When to write to us
If a store won’t quit, see The store is still running. Write to us if that doesn’t help.
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.