I believe the root of evil is the same for both: the hardware is too weak to handle more than a certain number of miners connections -> when this limit is reached, the stratum server falls off and miners start getting "connection refused" -> when stratum server goes up and miners resume working on the block, that block comes too late and the network refuses it (i.e. it becomes "orphan").
However, it's just my theory, I don't know what actually goes there.