If there is a loan fee paid by the loaning club (Everton) - then the loanee club (Lyon) is under no obligation to take the player back during the agreed loan term.
No oversight, just the machinations of loan contracts. It could be considered a duty of care for Lyon to take Mangala back to have his ACL injury treated by their own medical department, but it wouldn't absolve Everton of their salary commitments or their loan fee.
It's the same situation with Broja, but at least the Mangala loan doesn't impede our attempts to loan another player from outside of the Premier League.
