It may be just yet another symptom of not ovulating
The progesterone phase of your normal cycle changes the nature of the lining, stops proliferation and at the end when it drops, causes spasms which sloughs off the lining and close the blood vessels.
It would appear that around menopause, nothing works quite right
Have you tried taking ibuprofen for a morning? It is supposed to help stop bleeding. I think I have taken too much of it, with joint aches as well.
I have been fine on hrt, but have gone all haywire at the moment, since I went travelling and messed up my routine.