Problem solved! I've been stupid, some of the old steel needle was left in the thread which took some fiddling to clean it out but it's done now. Sorry for wasting time
No time wasted. It's always interesting to wonder why things aren't how you expect them to be. Good to hear the problem is solved and everything is as it should be.
Yes, nice you got that sorted out. If you want a new one to play with, might I suggest a 1020? Since you now has been "forced" to get so familiar with the 991, a 1020 is a good choice. Practically the same lantern, just a notch bigger. It will be a cakewalk for you to fix.