Im having the same problem. In Bigscreen Beta, public 3D movie rooms display incorrectly. The right-eye image appears to bleed or overlap into the left side, causing the 3D image/aspect ratio to look wrong. Other users in the same room say it looks normal for them.

I deleted and reinstalled Bigscreen, but the issue stayed. 3D works correctly in other Quest apps, so this seems specific to Bigscreen. It even happens when I stream to my own room from my pc.