• Set a villager to stand still and it will proceed to lag the whole server, causing massive tick lag.

Oh yeah, that does indicates what might be happening, not sure at all tho, on other notes, I quit playing Minecraft so you're on your own to figure this out from now on.

I can not reproduce that issue, how do you measure tick lag? Does it always happen? Do you have mods? Dedicated Server or Integrated Server?

I was playing the MCA mod with the Minecolonies mod, my goal is to build a colony that is also inhabited with various MCA. After I've hot the basic infrastructure settled, I decided to bring in the MCA villagers, I ordered like 5 to stand still in places that the colonists don't come to visit, after sometimes, I experienced massive tick lag that halted the sun and moon cycle, I then set the mca villagers free and the lag subsided, not sure if they were constantly trying to reach to their workstation some beds since I didnt register neither to them.

Comes to think of it, all these villagers are laggy as hell when used along with the Minecolonies mod since they follow the vanilla villagers claiming beds and workstation mechanic, they constantly emit green particles around them, indicating that they just had claimed something.

MCA Villagers do not claim beds, therefore the green particles refer to workstations. This is a good hint on what might be going on, I will investigate that somewhere in the future.