It could be due to the protection for the low momenta in the extrapolate function of GeaneTrackRep:
// protect against low momentum:
FitterException exc("GeaneTrackRep: PROTECT AGAINST LOW MOMENTA",__LINE__,__FILE__);
Since when you call gtr->getMom(lastPlane) you perform an extrapolation and in this case q/p = 10.19 the extrapolation could fail.
You could try to comment out the lines of the protection against low momentum to see if the problems disappears.