I don't know what to say because I'm experiencing the same problem. I'm working on a quilt with rather small pieces like yours. I am being so accurate and precise in everything I do. And seams just aren't matching up, points are disappearing.
I too have been sewing all my life and quilting about 13 years. You'd think by now I could handle the challenge. Mostly I sew quilts for kids. I have always tried to do my best on them. And for some unknown reason things match up on those.
It is terribly frustrating to the point I'm ready to put this project in the trash. I just keep asking myself "why are you doing this?"
So if anyone out there can help the both of us, please chime in.
SVAL