Well, W and I don't exactly have a "HoH" type arrangement, so that's less of an issue.
There are a few different ways that I might respond if I were triggered.
One is that I become something I'd describe as "willfully obedient." Even though I know that things feel wrong, and that I'm not in a good mental space for a punishment to be effective, I will stubbornly insist on just going through it, knowing that it won't make me feel any differently. I won't respond much to the spanking (or other punishment), and I don't resist--in fact, on the surface I seem eager to receive it... or at least to get it over with. It's a control thing, and it's some of how I coped when I was a kid--I knew the adults weren't going to listen to anything I said, and that they weren't able or willing to recognize how I was responding so long as I didn't defy them. They didn't care about how I felt, they just wanted to exercise power. So I let them feel they were in control, all the while knowing that my responses (or lack thereof) were what shaped the outcome.
Another way I might respond is by having a panic attack. Shaking, sobbing, sheer terror. That might happen when I was in a good mental space, and something went wrong, or it might be an outcome of willful obedience.
When I'm able to recognize that I'm getting triggered, and have the ability to act on that, I just let W know that something isn't right, and we step back until we can fix the situation. In our dynamic, we assume that neither of us is a mind-reader, and we trust each other to be honest. W might often have a good sense of what I need, but she's not telepathic. It's my job to make sure she has enough information to take care of me (and vice versa, obviously).
We tend to believe that something like me not holding still for a punishment, or otherwise resisting, means that something isn't working correctly. While it's a nice fantasy to be held down against resistance, in practice for us resistance is a signal that we need to change how a punishment is occurring.