Is it possible to have the software rev on the game where this incident happended verified?
Secondly it would be helpful to know if the player tilted out. Or was having game modes running at the drain before the incident. The behaviour of the magnet might (by mistake) be reset in a procedure that is omitted when end-of-ball is caused by a tilt. Or similar.
The key trouble shooting this, is, if the points awarded was indeed the Magna Force. In that case, I would say, try Magna Force with drain and with tilt. And in combination with other modes that utilise the magnet.
It is a common thing, that software bugs turn up in more unusual configurations or usage of stuff. Naturally right. Something outside of what the developement team and testing would normally circle. In pinball, special configuration, multi player games, export stuff, false switch inputs etc.
Or, simply by very subtle one-in-a-million timing and combination of state and events. Remember that T2 Super JP from PAPA finals some years ago.