Bless you what a stressful time you are having.
I can't advise you what to do - none of us can.
What I can say though is that you are not alone being in late menopause as I was almost 59.
I have had a series of scans over the last 2 years with different consultants as each found slightly different findings. I think this is normal as I was told that hysteroscopy is sometimes needed to really see what is going on. When I had the first hysteroscopy in 2019 the scan said my lining was 6mm but it was found to be atrophic and too thin to biopsy at the time of surgery.
This time I have had surgery as they had been monitoring what they thought was a polyp, but that has now been removed and I am waiting for the results but it wasn't a polyp but a possible fibroid.
I guess what I am saying is that the scan and the hysteroscopy don't always agree, but if your scan is showing nothing they are worried about your lining must be within the threshold and there can't be anything that concerns them.
My consultant told me that hysteroscopy findings are only valid for 4 to 6 months, so unexpected bleeding must be reported after clear scans or surgery especially after a few months has elapsed.
If it was me I would monitor the situation and if I had any further unexpected bleeding I would contact them. I know it is scary, I have been so stressed with it all but I would certainly do that.