Are all the moving parts very clean and moving freely ? Nothing worn ?

LTG : )

Test the the coil by connecting directly to power and see if it kicks well, if does it might be a dirty switch or weak solder joint or weak connection farther up the circuit.

Frenchmarky. I have exactly the same problem on 2 of my games. This is not the first time I have had this issue. I have replaced all my boards with Alteks and repined everyplug, I have replaced coils and entire mechs with still no change. I have my buddy CHRIS HIBLER coming by soon and once HE figures it out I will post . PM me and I can send you the fix. I have repaired /shopped /and owned over 1000 games in my 20 years and this one issue has always had me stumped.

The bally 'chimer' games (-17 games) all have a VERY short default pulse in the software for coils. They lengthened it by 66% when they went to electronic sound boards. This contributes to any issues with coils, connections, and mechanical issues. It has nothing to do with the outhole switch being dirty or anything like that; that's an independent circuit - it MIGHT have to do with the outhole switch wireform getting in the way when it's kicking the ball.

I'd try it with the apron off and see if you can see anything going on there. It's a really simple mechanism that hadn't really changed for years at that point. When you say it's a new unit, you mean the coil or the entire mechanism? Since there is metal on metal contact in the kicker, it's one of the very few things on a pinball machine that needs lube. It doesn't need much and if it had been lubed when it was installed there might be too much on there (or the wrong lube.... if it was WD40 that's wrong). The shaft needs a touch of lube. Honestly most of the time I just clean any old stuff off and leave it it's not going to wear much in home usage. Even in commercial usage I don't think it wears too much, I've never had to replace one on any machine, a good clean is all it takes.