<human>: Can you provide a brief rundown of the text in within 3 sentences?

I have been fairly close friends with this couple for around 8 months, and everything seemed fine until recently someone who knows them very well approached me with some concerns about the boyfriend being abusive towards his girlfriend.

Quick background: Both them and me and my partner are part of the BDSM scene, so a lot of our socialising is based around that (this confuses things a bit given violence in that context can be OK).  The guy used to (and possibly still does) have quite a few issues, including terrible self esteem and anger problems.  I had noticed a few things wrong, but nothing more than arguing.  Thinking about these in light of possible abuse, they could be worse but I don't know.

I met up with the person who approached me - he has recently badly fallen out with them but wanted to discuss it with someone still close to them.  He said that they had had some extreme arguments, and the girlfriend had been very unhappy.  He has tried to intervene but neither were at all receptive.  He says that after a very long talk the girlfriend admitted there were problems and was ready to leave, but about a week later they were back together and not long after moved in together.

My problem is that I consider this couple my good friends and I want to help if there is something wrong.  At the same time, I don't want to make anything worse if it's getting better, or if there's nothing wrong.  What do I do?
<bot>: Friends' relationship seemed fine but a mutual friend thinks maybe it is abusive and I don't know the best way to deal with it.