I assume that the PoW system has been designed in the way it controls itself. If the difficulty is too high and mining hash rate is low, then it takes more time to mine a block. The system detects that and adjusts the difficulty so the mining is easier. And vice versa.
What if the decrease in difficulty would be too large? Then the block generation rate would rise quickly. The system would sense that and next raise of difficulty would be so large, that it would be greater than it was before it was lowered. Repeating this would cause the system to go into resonant oscillations and it would cause the difficulty to go into level that it would not be possible to mine a block and whole system would overload.
Is the block mining system protected from such scenario?