Hello! Just found another bug.
Items that are not in full stack only swaps in inventory places when you try to combine them.
However, based on the results that I got when I tried to recreate the said bug, I have observed these results:
All types of inventory that needs the Inventory Window - Items in non-full stack just switched places.
Recreatable by: Splitting items into two non-full stacks of the same item, and try to combine them inside the inventory window.
Furnace - Not smelting a non-full stack of Iron Ores even if there is a non-full stack of Iron Ingot in the output slot.
Recreatable by: NOT RECREATABLE. It seems that it was only a bug when you just updated your world from the one created and last run on 1.11.0.3 and opened it again in 1.12.0.2. The bug behaved like it wouldn't smelt Iron Ores that is placed there in 1.12.0.2 while Iron Ingots from 1.11.0.3 is still in the Output Slot.
Items not combining in a stack can be solved by any of the following. This list contains all possible methods as far as I have observed:
Put items in a hopper and let it do the transferring. However, since it uses the Inventory window. you need to place the broken stack into it's 5 slots. If your items is more than 5 stacks, consider placing a chest above it and place the broken stacks inside the chest above the hopper.
Drop all non-full stack of the same item, then gather them. It automatically combines them as you have claimed a single item on a floor, and combines it on the stack of the same item.
When smelting, remove all contents of the furnace (if it's contents contain material smelted or created on 1.11.0.3), then wait for all of the ones in the Input Slot to get empty before putting up a new batch/stack, as they won't combine (unless a hopper supplies the Input Stack/Fuel Slot). Same with the Fuel Slot.
If more details are needed, or if there are more parts of this bug being found, I will add them as a reply/comment on this bug.
Linked issues
Comments
[Mod] LateLag
migrated
Actually, that workaround is what I mean in #2
[Mod] LateLag
Oof sorry. I missed that part.
migrated
I've got the same bug. Can confirm all of the things you said in this report.
migrated
There is a bit of a development on the bug look-up.
My brother can combine items on his device (which happened to be the same model and android version of my device), but he uses the Classic UI. No bugs have been present on that UI. When I tried to switch my UI to Classic, all the bugs were gone, but it comes back when I switch back to Pocket UI. I do use Pocket UI since only my brother have a wireless third-party xbox controller to play with Classic UI.
So far, switching UI is only an addition to possible workarounds to avoid the unmergable stacks of the same stackable item.
[Mod] Celesian
Thank you for your report!
However, this issue has been closed as a Duplicate of MCPE-44649.
I've added your description to that main ticket, as it describes the issue better. I have added it with credit to you
Please add a vote and any new information to the main ticket, which will be updated accordingly.
If you have not, you might like to make use of the search feature before making a new ticket, as it's likely that the issue has been reported already.
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I've found a workaround. You can drop both stacks in the same place and pick them up.