Connections issues with server, players timing out or connection reset

Around two days ago, server hosts experienced issues with their node's DDoS protection system, therefore i assume something was changed to fix it. Since then, some of our players have been unable to join the server and keep encountering this error. These players are from different locations worldwide so there's no correlation between region for effected players. They have tried everything from restarting Minecraft and their PC, updating Windows and Java, checking firewall settings, and resetting network protocols, but none of these seem to work longterm. If they do manage to connect, they eventually get disconnected again. We've also tried restarting both backend servers and proxy, giving them raw IP, deleting player data but any of this didn't help. These players are able to join any other server and their network otherwise is fine, they all seem to be Java. And there's also a part of player base that can connect just fine, including myself. Using a VPN sometimes helps temporarily, but players still get disconnected and have to switch locations. The only reliable workaround so far has been using a mobile hotspot. This was server provider response: "Hey there, the DDoS protection shouldn't affect the server, it could be your ISP changing their routes. I suggest using something like Cloudflare Warp to combat this issue." I don't fully understand why this issue suddenly started affecting some players when everything was working fine for months. Is there a way to fix this, or is this likely an issue on the provider's end?