Oskar
Are you hand tapping, or drillpress or using a tapping device that clutches foreword and reverse as you push or pull the tap. ???
It really sounds to me that you are having a problem with the tap itself and need to get a good quality one (get a few if you really are tapping a lot of holes). I think that I might have broken 4-5 taps in my whole life and I typically tap for 4-40, 8-32 and 10-32 fasteners. A cheap tap is just that, cheap. A good quality tap should make a bug difference, but get at least a pair just in case.