Sorry, forget about the .exe part, that does not apply to Macs.
This may be a bug on Macs at higher UI scaling settings. But we may as well try a clean reinstall:
- move any valued save games elsewhere, and user empire designs.txt from /Documents/Paradox Interactive/Stellaris/ if you have made any custom empires or races.
- "uninstall" in Steam-Stellaris
- manually delete both the Steam/SteamApps/common/Stellaris AND Documents/Paradox Interactive/Stellaris folders
- re-install game in Steam, run a Steam Verify when done.
- start the game with no mods active and test
In particular you need to make sure there are no files or folders left under either the Steam Stellaris or Documents Stellaris locations, before installing again.
**File Locations on Mac OS X**
The executable and DLC folder are in Users/USER/Library/Application Support/Steam/SteamApps/common/Stellaris/
To see it go to the...
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