Strange black spot on quads, only on mobile devices

I've been trying to port a game to Android. On Windows and the unity editor, everything looks fine:

But when I run it on Android, I get this really strange black spot, and only on quads (the road and background are quads, everything else are just 2D sprites). I've turned off cast shadow and light probes and stuff, but even then there isn't really anything that could cast a shadow. The guy isn't casting a shadow because when I move the character, the circles remain in the center while the spring camera shows the person moving.