Newly bonded rabbits grooming question

A friend of mine has recently adopted a female rabbit, Lola, for her 5 year old, recently neutered male Fudge. Lola has also been recently spayed, but was a stray and her age is unknown. They were bonded about 2 weeks ago and it was a straightforward bond with the bunnies coming together easily. They spend quite a bit of time grooming each other. In the last couple of days my friend has noticed that Fudge has a patch on his back about the size of a 10p where the fur has been nibbled short and the skin underneath looks dry with a couple of small scabs, but does not look red or sore.

Is it likely this has been caused by over enthusiastic grooming and if so should she try and put a stop to it? How would you actually stop the grooming, or cut it down?!

I think my rabbit got this. But it was the girl rabbit who was being kinda nibbled to stay still for being humped! hehe!

Might be similar kinda thing? Or maybe I'm the only person to have ever had this!

Hmm, I thought that too with the mounting thing, but it's her doing it to him!

Yeah I think that can happen... it's a dominance thing I think.

Where abouts on the bunnies back?
Could it actually be a vaccination site?