One drum Master's creasing on RISO MZ770

[adonnelly3]

Hi all, I'm really hoping someone can help me out with this.

I've got a RISO MZ770 and only one drum is having masters creased on it (see pictures).
There is a small lump on the edge on the drum screen (see pictures), this is on the opposite side to where it seems to crease, however this has never been a problem before?

The only other things I could think could be relevant is that I replaced the master roll recently? Also a rubber ban snapped on the master disposal, although the disposal never worked and masters have always been removed by hand? (See pictures)

Really hoping there's someone out there with some solutions?

Many Thanks,
Adam

[Iowatech]

If you haven't tried this already, swap the drums and see if the wrinkle problem follows the drum or stays in the same drum cavity.

[adonnelly3]

I tried on the other side but it was still creased. I noticed a little indent mark appear after this on the little bump I mentioned. I took the two screws at one side off, it then flattened, problem was then solved.

Thanks for the help!