Am I being stupid? Fitting new side repeaters,one won't fit

[sparks_E39]

Got some clear repeaters delivered the other day, tried fitting them today, one goes in no problems, the other just sits loose and can be easily pulled out, they are from a company called in.pro. The clips on the old ones look the same as the new ones and all the fittings look identical except for the BMW stamp, and the two new ones are identical in every way so I don't think they are faulty.... car is an E39 5 series.