Maybe this has already been suggested, or maybe you've already done it anyway, but it's worth confirming...
Have you tried playing a few completely different DVDs, unrelated to the set of discs on which the 'angle' thing appeared?
There's two reasons I suggest that. Firstly, it would be interesting to know if it only happens on some DVDs, even if it were several in the same set.
Secondly, I believe some DVD players manage to 'cache' information about the disc they are playing, to facilitate a faster restart if you need to switch off in the middle and resume later. Playing a few other DVDs may flush that cache. So it's even possible that doing so would get rid of the icon when playing the original discs again.
7LM