Leslie Andrew Roberts

Silent - I'm not so sure that this had to do with chunks unloading, as I've been affected but have my kelp farm/smoker array in a custom ticking area on a realm... Perhaps my issue happens when the realm goes idle though

Edit: I just looked up the difference in kelp xp vs mutton/iron. I still think it has to do with a maximum amount of xp that can be stored... Can you repeat the video with 9 stacks of iron, 18 stacks of mutton, and 63 stacks of kelp?

This appears to affect 1.11.4 also. I feel that it is an XP cap on smokers/furnaces. I have a mid level kelp farm(256 plants) connected to 7 smokers. For fuel I have a hopper and a single chest per smoker. So total capacity is 32 stacks of fuel which I obviously use kelp blocks. I filled all smokers up to capacity, which should smelt 41K items per smoker. I let about a third of the fuel get used up as I AFK'd for about 3 days... When I went to reap my massive XP reward, nothing... Fom any furnace. So I cleared out the fuel, adding only 4 stacks per smoker, and when this finally ran out it was great, XP and all as soon as I locked the bottom hoppers so I could pull out a single item - enough to fully repair an unbreaking III mending pickaxe.  So I threw 10 more stacks in, and when these finally ran out I got nothing again.

So I believe there is a maximum amount of XP a furnace/smoker(and probably blast furnace) can hold, and when this is exceeded you simply get nothing out of it.