I have had rams with a breeding crayon marking harness on and ewes on the other side of the fence, and guess what? Those ewes on the other side of the fence had to have been bred through the fence as there was no mark on them, and they ended up pregnant!!
I have had other people tell me their animals also got bred through a fence, so it is a possibility.
One time at round up time, we were sorting some range cattle, and a neighbors cow repeatedly jumped a 6-7 foot log fence. Most cattle won't even challenge a 5 foot fence, but some can do it if they have the proper motivation.
Maybe that is part of the answer to some mystery breedings..
Nite Hawk