Doing "Reset World" -> "Upload World" on a world slot that currently has a resource pack (eg, an adventure map or experience) will bring the previous world's resource pack into the new one that was uploaded. This also seems to be linked to upload failures.

Not super critical as it can be worked around. Replacing the world containing the resource pack with a fresh survival world will clear the resource pack. Uploading over that fresh world will make everything work fine.