clutch in the bin
Join Date: Mar 2009
Location: United Kingdom
County: North Yorkshire
Certainly does sound like a dodgy replacement unit but I may be wrong as these things can just happen without obvious reason.
Did the problem with the original unit occur after bleeding the brakes / draining the braking system by any chance? That could point to the original ABS unit needing bleeding - activating it via fiat multiecuscan as air locks can occur in the ABS unit. Not sure of your level of knowledge so apologies if you know all this already, but if not, search on this forum about bleeding brakes.
No ideas I am afraid beyond this point.