Probably pretty common, at least for short periods of time. Self-preservation.
There's healthy respite, where the parent does some self-care to regain strength and be able to deal with the challenges in as healthy manner as possible.
But there's also, in my experience at least (unfortunately), extended periods of avoiding difficult child at all costs, *not* doing self-care but just trying to pretend the problem isn't there, that is in my humble opinion counterproductive and damaging to the entire family.
It's all about balance.