1. Craft a set of scaffolds
2. Make a pillar of a few scaffolds (I did 4)
3. Break the bottom one
4. Pick them up

One of them does not stack with the rest. That one will drop as an oak scaffold regardless of the original scaffold type.

Thanks! I'll look into it.

I made a quick video: https://youtu.be/IFuU3cGw4Ag?t=16s . The last 16 seconds are relevant to this bug.