About another colleague on his team slagging him off to me?
I work in a tech env where we have teams. Work is sent to our teams to develop. Colleague a) does my job (product owner) and colleague B) does a different job (team manager)
I feel I have a natural affinity to colleague a as they do my job and I have lots of meetings with them (and generally I get on well with them). Colleague B not so much. I find him defensive and troublemaking and quite sneaky.
We have an internal messaging system and colleague B has randomly sent me a message saying that colleague A isn't doing his job properly. Made an allegation. But it was in quite mean/critical words.
I have investigated briefly and found this to be incorrect. But I am now in the position of wondering if I should keep my head down and not say anything or wether I should warn colleague A that colleague B is saying things behind his back. I feel that if he is messaging me about it he must be messaging others about it too (as I am not close to him).
What should I do?