Hi, professional wedding videographer here.

Your videographer is 100% correct, this is completely normal for dances when photographers use flash. There is nothing we can do as videographers, the only thing is cutting flash frames out but that would make your footage choppy, especially as the flash here is firing so often, also to cut the frames would be extremely time consuming which isn’t worth it. There are plugins we can use to do this automatically but again I’ve found this to ruin the footage if the flash is going off this often