I had this issue on a self-hosted server (running on my local network) but had nothing to do with multiple players, since I observed this far more often when I was alone on the server. Ended up bailing on the server, running locally and nerfing raids entirely with devcommands. Having one or two raids every day I'm playing was just not making the game fun. I will note that this only started after I wiped out Bonemass in my new server save after the update dropped.