You could start by having Steam verify the game files. Someone else recently had a problem getting a different minikit and verifying the game files apparently fixed it.

I finished the game years ago, so I don't remember much about that specific part. If you've checked videos/walkthroughs and you're sure that you're doing the right things, the only other thing that I can think of is to make sure that V-Sync is turned on. Playing without V-Sync can cause various problems in this game, although if that was an issue for you, you probably would have had problems long before you got to that point.

i did it (verified game files and turned v-sync) and i didn't get nothing until i launched game via testapp.exe. when i did it, everything worked normally

That's weird, because LEGOBatman.exe and testapp.exe are exactly the same. I don't know why there is a testapp.exe, but it's identical. I wonder if it's because you ran the EXE directly, instead of (I assume) starting the game through Steam, or if maybe something on your system was interfering with LEGOBatman.exe, but not testapp.exe ?

IAC, I'm glad that it worked for you.