Have your suvivors put enough fish in it before?
doesn't matter they just get stuck in that motion where they continually try to put water into the fire no matter how many fish are in or not
Happened to me too, so many times. The only way I could avoid this glitch was by assigning them other tasks like demolish, fishing, cutting and etc. However, right after that, they would go back to carrying water back and forth without doing much work. They wouldn't build or repair structures.