This appears to be a known problem on this forum but no conclusive solution
I have checked the levelling of the playfield
I have adjusted the microswitch
Using ROM version 9.4
The balls eject well during solenoid test but the pulse is too brief / too weak during gameplay.
Apart from waiting for a ROM update I have bought two coils to replace the 27-1200
I have a 25-1000 and a 24-900

Before I start this repair - is there any reason why I shouldn't put in a stronger coil. Will there be much difference with the 25-1000 or should I try the 24-900 first?

Firstly I tried the 25-1000 coil. In test mode the eject was so powerful it hit the top bracket and the ball bounced back into the hole. Worked okay during gameplay so I can live with that arrangement - but still struggled if two balls are queuing up in the eject hole
24-900 coil solved the problem altogether - balls eject whether one or two queued up in the lock hole.

I do have a question - as I haven't played this game fully working - when I lock a ball it is then released and I lock it a 2nd time, again released.
Then the left ramp shot starts multiball - everything fine.
I was expecting the game to have a captive lock - I don't ever recall coming across a game with a non -captive lock - or is this an option on the machine or something else gone wrong?