205 6 speed Diesel??

[OW1989]

I have briefly spoken to the previous owner and he isnt sure (always helpful) but thinks the driveshafts may be 306 ones because he used longer 306 wishbones. Would he have had to change the diff over to fit the gti6 box? Literally just seems like the splines are not fully going into the inner cv joint and they are slipping when driving. Almost as though the intermediate shaft and bearing need to go back a tiny amount towards the hub