To replicate the glitch:

1. Get a smithing table, 2 random armor pieces (they need to be the same), a random template and a random material (for the armor trimming's color)
2.  Trim one of the two armor pieces with the template and the material on the smithing table
3. Equip the armor piece without the trimming using right click (try to mine a block with it to equip it on mobile)
4. Equip the trimmed armor piece with the same way as on step 3

You should have worn the actual trimmed armor piece but in your hotbar you still have a trimmed armor piece (but if you open the inventory it won't indicate that it's trimmed and if you were there will be no trimming whatsoever on your armor on your player model). This bug can happen in multiple ways, not just with the steps above. For instance it could also happen when swapping the two armour pieces.