What kuririn said. Dirty clips will really affect things. Put an emery board in your flight box and use it to buff up the clips from time to time.
When Q-Jets were new one of the things that I tried was to see if the little Estes Astron II controller (which uses one of those little 9V batteries) would fire the supplied initiators. And yes, it would. So yeah—dirty clips and/or touching clips were probably to blame.
Aerotech has beefed up the initiators just a little and are trying to package them so that they don't get damaged (this is mainly an issue with bulk packs, but is also in the spare initiators boxes) but I also can say, from experience, that a FirstFire Micro with the pyrogen knocked off so that the bridge wire is bare will fire both the FJ and W Q-jets, at least on a PSII controller with a 3s LiPoly inside.
That heat shrink is, of course, the stuff you're supposed to use, after sliding it off the initiator, to hold it in the motor's nozzle. Orange is more recent...it might be just a touch smaller in OD, which will work better in As and Bs. The red/pink is OK in Cs and slides right in alongside the initiator on Ds.