The progress arrow in a furnace, smelter, or smoker stops updating at random points. This does not affect the actual smelting process (1 coal smelts 8 items, for example.)
This happens whether or not player leaves the area.
Two example screenshots attached.
Progress stops during the actual smelting process, but progress indicator does not clear when items are removed. Putting more ore/food AND fuel in resets the indicator, though.
Thank you for your report!
We're actually already tracking this issue at MCPE-63099, so I resolved and linked this ticket as a duplicate.
If you would like to add a vote and any extra information to the main ticket it would be appreciated.
If you haven't already, you might like to make use of the search feature to see if the issue has already been mentioned.
Quick Links:
📓 Issue Guidelines – 💬 Community Support – 📧 Customer Support – 📖 Game Wiki