this electronic arcade tabletop pinball is fantastic!

This is not working right. Either you need to use rechargeable batteries or the gear on the motor is cracked/slipping. Cracked motor gears are unbelievably common on old toys using the hobby motors.
The bumpers have no power. It's a fairly simple mechanism. Mine had 2 problems. The gear fell off (though surprisingly it didn't crack) and the motor wasn't spinning. But a cleaning of the motor and putting the gear back on fixed it. Cleaning the mech helped too.

Intresting as I didn't realise that there was a different version of the Modern one, it's a shame they didn't carry over the Bumper lights from the other clone as some flashing LEDs from impact with the classic looking Bumper caps (think like the Space Cadet ones) and it'd be perfect.
The Stickers even when present leave a bit to be desired as mine actually tore during application which was a bit annoying (it was brand spanking new from a toy shop so hadn't been sat in damp or anything) but theres always scope to have a custom set made and even maybe change the play field graphic.