[Tannaton]

Its been said but the propshaft is balanced as a discreet assembly, despite what some manuals might say (including Haynes) there is no requirement to mark the flanges when removing or put back the same way. If you were splitting the propshaft to change the centre bearing - that would be different.

I'd check the flanges are mated correctly and all bolts are correctly tight, including the centre bearing carrier.