Newcastle United fear AS Roma are attempting to re-negotiate the fee due for Mapou Yanga-Mbiwa.
The French international impressed during his loan spell with the Serie A outfit.
But he was surprisingly left out of the side just three games short of the agreed 20 appearances mark which would have triggered an automatic £5.5 move to the Italian capital.
Toon officials suspect Roma took the decision in a bid to negotiate a lower price, says the Daily Star.
The 25-year-old struggled to hold down a regular place at St James' Park before moving last September.