Minecraft server with TOO MUCH RAM?

Hi, I'm a supporter at a Minecraft server hoster and recently I've been getting more and more tickets where customers even with 64GB RAM have lags. (The RAM is of course never completely exhausted) Independent of the version, with mods, without mods.

Could it be that the MC server can't handle too much RAM?

I don't think so but it just happens more and more…

Maybe machines were simply built on the servers that can lag the server. Or the players simply didn't allocate enough RAM to Minecraft themselves.

Either the players did not have enough RAM allocated or the server was overloaded.