DElyMyth

Affected all villagers in my world, both employed and unemployed.

I left all doors, just removed some villagers, still have 300 wooden doors at that place, but just 24 villagers.

I had the same issue with around 100 villagers in my iron farm, left all the doors there, just removed the villagers and the situation is back to normal with less than 16 villagers.
Block lag is still ok with 24.
All 300 doors are still there (it was too much of a pain placing them to remove them 😛)

Do you have villagers?
I noticed ticks skip starts when my villagers at spawn go up to around 16-20, with more than 25 (ish) the block lag makes the world unplayable, until I kill some villagers to reduce population.

Same issue. Noticed that avg. tick when the world is loaded on server keeps increasing its value, getting above 300ms, and the server was acting like this also when I wasn't connected (launched server, went for a smoke, found this):

[21:21:03 WARN]: Can't keep up! Did the system time change, or is the server overloaded? Running 8478ms behind, skipping 169 tick(s)
[21:21:59 WARN]: Can't keep up! Did the system time change, or is the server overloaded? Running 47329ms behind, skipping 946 tick(s)
[21:22:10 WARN]: Can't keep up! Did the system time change, or is the server overloaded? Running 10572ms behind, skipping 211 tick(s)
[21:23:22 WARN]: Can't keep up! Did the system time change, or is the server overloaded? Running 61174ms behind, skipping 1223 tick(s)
[21:23:33 WARN]: Can't keep up! Did the system time change, or is the server overloaded? Running 11354ms behind, skipping 227 tick(s)

Singleplayer does more or less the same.