Weihrauch 30s .177 Stuck pellet

Just as the title reads. I was shooting my Weihrauch 30s today and everything was going great. After about 20 rounds I went to shoot it again and it was loud and I could smell something like ( dieseling ) ? Managed to get the stuck pellet out with a Tipon rod and the skirt was slightly deformed. Any ideas what caused this and it it safe to shoot again. ? The pellets were SigAir Flat 7.71 gr. Thanks
 
My HW 50 Didn’t come overlubed. So no dieseling at all. It was a refurbished gun from pyramid air . So maybe they had it apart and cleaned it up. It looked brand new though when I got it. Any other break barrel I have had though came overlubed And Dieseled For quite a while.But for a pellet to stick in it,Either the barrel was very dirty or that pellet was bent pretty bad.Or a combination of both. I use H&N 8.64 grn.pellets In mine because they shoot accurately but they are pretty tight when I push them in the chamber. - Now reading what Long Gun Dallas said about the piston seal going bad from the dieseling, I never thought about that but he is probably right. Losing compression would do that.Also check your breach seal by putting a piece of toilet paper on the top and seeing if it blows it off when you fire it. That’ll make it low on power too. You need to check and see how many FPS you’re getting with a chronograph. That will tell you something right there also.