Interesting one this evening. DH doesn't take ADHD meds at weekends, and is also feeling run-down coming down with something. Unfortunately he tried to do some maths with DS this evening.
I was upstairs when I hear some shouting downstairs and DH telling oldest DC not to interfere and that he's just making things worse - evidently DH was getting short with DS and DC made a comment or got upset.
Later I come down and DH is angrily demanding I tell DC to 'butt out and stop interfering' and I said I can't say that, I can't say what he defines as 'interfering', I understand why DC might have said something, even if he might have been getting ahead of himself, he was just being protective of his brother. That led into an angry spiel about 'how can he trust me when I always undermine him about things like this' and as usual with this I said sometimes I cannot back him up because I don't agree, and some argument. In the end, I calmed down, said I'd talk to DC but I couldn't guarantee I'd give the message the way he wanted.
So I did talk to DC, I decided to tell him to come to me if he is concerned about an interaction and let me deal and don't come in too soon (TBF, occasionally DC can be oversensitive and starts getting upset when DH is justifiable cross with someone and tries to de-escalate when he doesn't have to ). I came down and told DH this, by which time he'd calmed down, and told me DC can totally tell him what was wrong with an interaction after the event and he'll take it on board. I told him 'Look if you'd said that to me in the first place, that would have been fine - you'd have given me a reasonable, meaningful thing to come to DC with and I wouldn't have pushed back'.
DH agreed that it's notable that this generally hasn't happened since he's been on the meds, so it's definitely an ADHD outburst thing.