Claymore 11.7 watchdog not working.

This is the 1st time ever happened to me. Normally, when gpu shows hashrate at 0.00 mh/s for about 1~2 minutes, watchdog would catch the crash and restart the miner by default.

Last night after epoch changed to 190, one of my GPU (RX580 8G) crashed during DAG generation. So the hashrate was 0.00 mh/s, the only difference this time was it stayed at 0.00 for 2.5 hours or so, watchdog never caught this crash even the hb time was 418109 (normally watchdog restart the miner when hb time > 20000). Eventually I caught the error and restart the miner on my own. Watchdog was very reliable in catching crash and restart miner in the past, but this time it failed. Why?