Furnaces will at times, not give experience, both with hoppers and otherwise.
However, furnaces appear to "reset" if broken, picked up and placed back down, once again giving experience for some time before stopping again.
Comments 2
Cleaning up old tickets: This ticket has not been updated recently (~1 year+) so is being closed as Cannot Reproduce. If you feel this is still a valid issue then please comment, or create a new ticket following the Issue Guidelines.
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i have found the same problem and its if you leave the area and they get unloaded or if you log out