i have bought 3 discs from 3 different sellers so far that skip during the credits, and one of them was sealed! i think someone here mentioned this problem once, idk, but i'm pretty surprised this would happen to me 3 times, i dont get it

Sounds like your player is out of alignment and can't track on the outer parts of LaserDisc's.

In my experience, poor tracking alignment will cause this on discs which are close to the limits of the specification, or in bad cases near the outer edges of discs (28~30 minutes in CAV — much less common on CLV discs) which are pretty much nominal. A good tuneup cures it except on discs which are genuinely defective. You can always try them on another player.

This behavior can be caused by a microwarp at the edge of the disc when it is encoded in CAV. In CLV, the microwarp typically can be compensated for by the optics since the disc is spinning at only 600 rpm when reading the outer tracks. In CAV, the microwarp causes too much jitter and the pickup looses track for a split second.