Try to get a log from the other player(s) if possible.
There are a ton of bugs that get reported, and it's a small team of mods. Be patient.
Is this a world from 1.12 or a new world? Also, do you have a crash log and were you able to reproduce the event?
That doesn't really make sense from a design standpoint, but okay
-Dried kelp has to be smelted. Much like charcoal. - My bad, thought you were talking about the kelp item itself.
Can confirm for 1.13