I can duplicate copper ingots.
Create world in 21w16a
Get 16 copper ingots
Craft them into blocks
Update to the newest snapshot
Craft them back into ingots
You will have 36 ingots.
Linked issues
relates to 1
Comments 3
Relates to MC-213630 but not the same issue.
Not a bug, for the same reason as MC-213630.
Can confirm