You have indeed given a very nice elaborate history.
From your history, the first three causes of bleeding that came to my mind are:
1. Recurrence of your cancer with some metastasis (secondaries) in the vagina.
2. Granular tissue at the top of vaginal cuff.
3.
Urinary fistula (tract) into the vagina.
Since, you had
cervical cancer 9 years ago, anybody will first think of recurrence only. However, after 5 years you were declared as cancer free. Recurrence after 5 years is indeed very rare.
The top of vagina is sutured during surgery. The suture line sometimes develops a granular tissue which bleeds off and on. This seems to be the most likely cause of your bleeding.
The urinary fistula is unlikely since the bleeding has now become brown and the doctor has already checked for it.
If it is a granular tissue causing the bleeding, simpler methods like cauterisation (burning the tissue) should help you.
The other gynaecologist will probably guide you properly.
I will be interested in having a update from you.