The only fault i could think of the linkage having was it either flexing to much making it pop the clip off the top, though the movement should be the same as the old one as it only moves into the same positions. Or the nylon bush that sits in the linkage may have a thicker top lip makeing it sit a tiny bit more closer to the cap and popping it off.

The only thing i can think of doing is comparing the bush to one at vauxhall and if they are identical, buy another clip and see if the same thing happens

Corsa C 1.2 , 02 plate.

Got a new gear linkage off ebay last week as the one on the car was the old plastic type and was worn. Respected buyer who sells alot of them.

Fitted the part, but had to buy a new top clip from vauxhall, (the cap type clip with four snap on clips round it) as the one that came with the linkage was broke.

Got the clip from vauxhall and put it on and it clicked into place and i could not move it at all.

Today, one week later after fitting i was driving along and the clip came off resulting in losing gears, i almost lost the white nylon bush that sits in the linkage aswell.

What could be wrong,
do you think the clip was faulty,
wasnt pushed on properly,
could there be a fault in the linkage some how maybe the bush being to thick or something.