Bonanza - most smokeless powders need to be very close to, or actually a lightly compressed load in large straight sided cases for good ignition. some allow leeway, of course.

Curl - have you tried or worked up any loads with AA5744? It is very much less critical for powder position & works well in reduced volume loads. It might be worth trying.

Lately, in the last several years anyway, I've switched from IMR4198 to H4198 in those rifles which use this powder. I don't know if that would make any difference in your gun, though as to ignition.

Hangfires are to be eliminated, of course. Very dangerous, as you know.