Steps to Reproduce:
Get a farmer villager next to a composter;
Give them seeds;
Wait and observe.
Observed Results:
The farmer uses multiple seeds at the same time, making multiple levels appear instantly. This also occurs when taking the bonemeal out, The villager will collect it and put more seeds in at the same time.
Expected Results:
The composter's level goes up gradually, similar to the player's interacton with it.
Screenshots/Videos attached: Yes
Notes: This can also seem completely random at times, so it's a bit difficult to reproduce.
I haven't seen the seeds being composted issue, however I have seen villagers pick up bonemeal. An easy way to reproduce that, trap a villager next to a composter, start filling it up to produce bonemeal. The villager will pick it up faster than the player can.