12 month old still vomiting post-revision

We can’t seem to figure this out (we being two experienced peds neurosurgeons and a flock of residents).
I brought brought my 12 month old (vp shunt since 2 months old, s/p prenatal stroke) to the ER after sudden onset of vomiting on Friday night. It was determined to be a valve failure so they replaced the valve on Sunday morning. He had a restful night that night and a happy, playful morning the next morning. He seemed very much back to his baseline except somewhat for a somewhat decreased appetite. We left the hospital at noon and within 15 minutes he was vomiting every 10 minutes, lethargic, totally back to the symptoms that brought us to the ER. We literally drove from the hospital parking garage around the block to the children’s clinic parking garage and went in to be seen. He couldn’t keep any fluids or liquid pain meds down all afternoon so they readmitted us and by the time we got up to our room (5pm or so) he was back to talking, smiling, feeling apparently good. Since we’ve been inpatient overnight, he’s been fine. (He’s had IV fluids, zofran and pain meds). He’s had 4 MRI’s since Saturday morning (it’s Tuesday morning now) and they’ve all been pretty similar in terms of ventricle size. His surgeon said she didn’t take off much fluid but there was significant pressure behind the valve that was alleviated by replacing it. I think they’re going to let us go again but I’m wondering if we’re going to end up in the same situation.

Somewhere I read on this sub that someone’s child was getting motion sick after adjustments to his/her shunt and the ride home from the hospital/clinic was always hard. Anyone experience this? Any thoughts about how you (as an adult or memories from childhood) feel post revision? Just trying to figure out if post-revision nausea in something we just need to get through or if it’s something that always means something else is wrong.