The £5 is positioned in such a way they you really think it will fall when in fact it won't. Eventually it may give, it would be illegal if they rigged it to never fall but unless people report this practice, it goes unnoticed. It is possible they can get caught with snap inspections but I think those inspections are very rare if at all.
Had a spare half hour. Haven't been in an arcade in a while so went on the coin pusher. Only threw away £2, I know they are rigged to the houses favour. Not only do the trays have raised lips to make it harder for coins to drop, they have their "banks" either side that goes to the owner. And they have dip switches to also control payouts.
These ones on Worthing pier are set just right as they "appear" to pay out a lot to keep you playing, sometimes dropping coins when not even playing. This creates the psychology of "I'll give these free coins a go. Oh look, that £5 is on the edge" and before you know it's you've spent £6 try to get that £5 note.
Got no objections to these machines, they are fun. But don't let YouTubers fool you in believing their is a "system" to beat theses, they're isn't.
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https://www.youtube.com/watch?v=4vfIxjkVoOk