Kinetic friction opposes relative slipping
The mistake
Drawing friction opposite the object's ground-frame velocity instead of opposite slipping at the contact.
Why it feels right
Friction is often summarized as 'opposes motion,' which is too vague.
How to catch it
A block on a moving belt has friction drawn opposite its ground velocity without checking belt-relative motion.
The first principle
Kinetic friction opposes relative motion of the surfaces at contact. On a belt moving faster than the block, friction on the block can point forward.
A package lands on a conveyor belt moving right. Initially the package is slower than the belt. Which way is friction on the package?
Common wrong move
Left, because the package moves right.
Correct
Right, because the belt surface slips rightward underneath it.
Make a fresh prediction before referring to the worked example.