Blocks not accepted

I’m using my own node to mine to and recently I started getting rejected blocks. Found the error in daemon logs and it says “E does not have enough proof of work: <621c21f18b96d3ee32e5d490cd59dae8fa3c1b510f3fae494d303ae440e30acb> at height 421699, unexpected difficulty: 14978875924”.

I’m using latest xmrig-proxy and xmrig to mine, spend key and wallet address are correct, wonder why suddenly I get tons of rejected blocks? I changed nothing about my config, same as when I was getting accepted blocks.