Something strange happens with my miner's monitor

I use Claymore monitor 3.4, miner version 10.0
1 or 2 rigs are constantly loosing connection with monitor. I.e. Monitor turns red and in "lost" state for corresponding miner.

While miner actually works (with pool) but with message:
ETH: GPU0 28.009 Mh/s, GPU1 28.529 Mh/s, GPU2 28.366 Mh/s, GPU3 27.995 Mh/s, GPU4 28.001 Mh/s
server: bind failed with error: 10048 (port for remote management is busy, use different -mport value), next attempt in 20sec...

I tried different -mport values but it doesn't help. It happens since Saturnday. I use read-only mode and internal IP