As a Wildcat mag is first inserted, it needs to be clicked to the next slot.

In a demo rifle, if the supervisor omits to tell the punters to do this (it takes about 0.1 seconds), then the probe and/or indexing arm is likely to eventually get bent or blunted, causing the failures you described.

Also the mag doesn't like taking or feeding flathead (eg RWS Hobby) pellets.