These are just shots in the dark, especially since the game works some of the time, but here are a couple of things that you could try (if you haven't already):

First, have Steam verify the game files, just in case you have corrupted game files. That seems unlikely if the game works some of the time, but there's no harm in checking.

Temporarily disable your security software and try running the game. The security software could be "blocking" the game (although, once again, that seems unlikely if the game works some of the time).

The only other thing that I can think of is basic stuff, like new/different video card drivers.

Be sure to enable vsync for LB1 and also enable it in your graphics driver. Otherwise I have not had issues other than modest coil whine only during load screens.

Hey dude did you fixed it? I have the same problem on every other lego game I own. Kinda annoying, please let me know.

yk like this has been a whole year and all but I find the fix go to C:\Documents and Settings\<username>\Local Settings\Application Data\Warner Bros. Interactive Entertainment\LEGO Batman and then open pcconfig.txt, change ScreenWidth to 1920 and change ScreenHeight to 1080, change WideScreen from 1 to 0 and save after saving right click on pcconfig.txt and click Properties and make it a Read-Only file and then done. (I'm putting this here since I don't see any viable fixes even on reddit which is surprising.)

Thank you Azor that just worked for me. Lol as you said, year later but, for others, I'm on Windows 11 and it started doing this when I hooked my ROG Z1E to my OLED 4k. I figure somewhere there caused an issue. I could hear audio but no picture.

Anyway, just an update to what I had to do.. the path is now: C:\Users\<username>\Local\Warner Bros. Interactive Entertainment\LEGO Batman

Everything else was the same. It was already set to 1920 by 1080 but setting the widescreen to 0 and setting the file to "Read-Only" sorted it for me.