I have multigrain loaf with a large amount of hot soaked grain that continues to tunnel, lately more and more often.  At first I thought it was due to undermixing, so I added 2 min to mixing time, but then it goes too far and the flax and bulgur start to tear. In process of elimination, I started folding more (instead of mixing), increasing to 4 folds, from 2 and increased the bulk ferm.