Apparently we have lag machine on our server, it keeps coming up and crashing people. It was always built at the top of map and it was a small like 15 times 15 blocks redstone circuit on one block platform.
The circuit was built off a short line of repeaters, possibly comparators and those were hooked to hoppers, droppers, dispensers and pistons.
I don't remember exact shape as it crashed my Minecraft client instantly.
The idea would to then remove it or even better blacklist it as it will make your server unplayable. Also it looks like this is only affecting latest Minecraft clients so 1.13 and higher for some reason.