Thanks for the report! I haven't been able to reproduce this. A few questions:

Does the Consume Skills target have a skill value that's greater than the corpse child's for whichever skill is being reduced?

Can you confirm the corpse child's "Learned level" for the skill in question is reduced when this happens? If you hover over the skill, it will show all the modifiers and the overall skill might appear to be 0 before and after consuming skills, but the "Learned level" is expected to increase.

Does this happen when the target is a dead pawn, or a downed pawn, or both? The Consume Skills behavior works a little differently for dead pawns vs downed pawns.

For what it's worth, that log seems to indicate a conflict between the "Corpse Children" and "A Rimworld of Magic" mods. Not sure if that's relevant to this issue, but might be worth seeing if this happens when that mod is disabled.