Is the ball channel height adjustable to give the ball more of a slope to roll on?  Just not enough momentum for the ball to get through

Naah, its straight on playfield unfortunately

I would suggest playing around with the switch the ball sits on, see if you can move the apex of the wire (more behind the ball) so it kind of gives the ball a helping hand through from stored energy in a compressed spring
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Hope you know what I mean.

Might be enough to stop the ball getting jammed.

edit: watched it some more - see if you can play around with the mechanics a bit more to stop the ball geting kicked back while the plunger energizes.

I know what you mean re the switch...If one of the other BH owners could take a photo of their switch that would help heaps (in case mine has wrong type in it)...Mine is the 1/2 type similar to that in the lower out lanes - but not the same as the top center lanes.

The actual mech is like new, not binding at all, lubed and not worn....