hey, i'm playing 1.12.2 on a server with the version 1.12.2-0.10.735 alpha of minecolonies, also i have a mod to have stack larger than 64 but it has never caused any problems (only graphical on the request), my buildings are almost all level 4.
i encountered bugs like the builder making request for items that he no longer need (he gets stuck on it), i restarted, fired him and make a reboot of the server but nothing work. (in addition there is no fullfill button)

also, i have a problem with the miner who doesn't make request and don't work, i did the same steps and that doesn't solve anything, after a long time the request will appear but it often does.
(the miner has been doing nothing for a while on the screen)

So when you cancel the request of the builder what happens?

sorry for the late response, when i cancel the builder's request it turns it off but only temporarily, it comes back after a while and he doesn't move from his place

I believe a /mc rs reset should fix most of your problems.

The request system seems troubled in this case. I can't reproduce it.