Ok this is the last issue on my NIP-IT...
It operates perfect except for the bonus reset. When the bonus unit resets ok in a rare case, it adds bonus correctly when it should and bonus is awarded correctly on multiball start or end of ball.

My problem is in the reset circuit. It resets and starts a game.
But normal operation is (I think) that the bonus unit is reset on a new game, new ball, new player, ... and a 1000 is immediately added by default.
My machine does run the sequence on reset, and I see the coil activating for the reset on the bonus unit. Which is immediately followed by a coil pulse for the bonus step up solenoid.
If I ad another player immediately I see the same thing happening in the sequence.
If I add a 2nd player half way a game with some bonus build up (still in ball 1 on player 1), the game leaves the unit ok (does not reset it) which is as it should it think.

--->>
However my game does not do a fully step up to the 1000 after the reset. It seems like it's just not strong enough and doesn't make it to reach the first thousand.

If I do it manually from the zero position it steps up correctly and I can play correctly. Bonus is added when hitting target or crocodile lane.
If the stepper did not succeed in going to the default 1000 on ball start. It doesn't add bonus in normal gameplay when the target to add bonus is hit.

Things I tried:
-cleaning the wiper on the bonus unit
-adjusting the 3 switches on the bonus unit. The one that is closed when bonus is just reset and is opening as soon as 1000 is added. The one that
-the one that is open in the bonus zero position but closes when the first 1000 is added
-the one every time the step up solenoid is triggered that opens during solenoid activation

In the reset circuit the bonus step up is triggered from somewhere. Perhaps I have a dirty contact there?
Or anything else that I should check. Maybe the switches are not set correctly when I bought the game.
Maybe the wiper doesn't go to the full bonus 00 position (but the zero reached leaf switch is closing?)

I have the schematics and studied it for half an hour, but I still have difficulties the way I should read sequences.

Thank you! I will doublecheck those 3 switches, clean/adjust and report back.

Thank you for the score motor switches info, I figured it worked that way but was actually ignoring that part of the schematic, because I didn't know where to start counting (right to left or vice versa)

Been trying for an hour this evening and I now I have a better success rate. But not 100%.

I first discovered that the stepper wheels reset position was not in a 'full position' at the wheel it's teeth, actually a half one.
Meaning that the first solenoid step up had to grab the stepper disc a little further (1,5 teeth) to be able to successfully 'pull' it one step up.

So I adjusted the iron arm (the disc reset position rests on) in a way that when the solenoid reset/step up is triggered, it is positioned correctly.

I discovered I can simulate the stepper combination with the reset relay, which makes it easier for testing.

I cleaned/adjusted the bonus unit zero switch, I cleaned and adjusted the two switches on the ball index relay that are closed during the reset sequence.
I cleaned 10A on the score motor.

But no 100% success...

I noticed however that when you play and have like 8000 bonus, often the bonus is not reset completely when you lost your ball... it ends up sitting at 2000 or 3000, and then the game is awarding you the extra 2000, 3000, runs the reset again and then the bonus unit goes to full reset.

Does this mean my stepper wheel reset spring is too soft, and I need to give it one extra turn? Or is disassembly and cleaning of the bonus unit advised?
This could perhaps mean that the wheel is not always resetting completely or not pushing 100% with force against the bonus unit zero switch?

Or do I have to look at SCM 8B (bonus unit reset switch) that is making clean/long enough contact?

That's the thing... stepping by hand works flawless... it's just the reset sequence that is happening too fast.
I'll guess I'll try to clean first, making sure it resets completely so I can be sure the unit zero switch is always pushed completely.
If not increase tension by adding a turn to the bonus unit wheel reset spring.

That is indeed a very good test to exclude what could be wrong or right. Thank you for the input.
I'l report back when I open the machine tomorrow (or thursday)

Ok almost perfect now!

I took apart and cleaned the stepper unit (the step up solenoid had some grease in it)..
I added one spring turn on the stepper unit return wheel.
I cleaned 8B on the score motor.
I correctly adjusted even more the bonus unit zero switch (this was the the most important change to my feeling)

It works far better now. Once a while it would still fail
I've uploaded a video.

The only thing I clearly discovered is that the score motor on this nip it turns a lot faster than on my other nip it.
Could this be a problem that the reset and step up is a lot closer together in time so sometimes mailfunction this way.
Can a score motor speed be adjusted?

Edit: I checked and found my game to be connected to lug 2, meaning "high tapped" I guess. Should I change it to lug 4 for low tap? What is recommended?

I will adjust my flippers a little higher

Game now on lower tap, plays better (not so fast), little difference but the problem still is there..

Will have to further investigate those solenoid step up switches

Another question:
when you push and hold the grabber button, I thought the logic thing to happen would be that the power would be cut trough the end of stroke on the grabber unit that is connected with the relay.
However it seems that powering the button directly activates the grabber relay.. so this means you could burn the coil by holding the button? Or is this coil heavy enough for that amount of power?

Thank you MarkG for the explanation on the motors and confirm the logic on the grabber.
I always thought, why would these be removed from the game as it doesn't drag on the playfield. But this will for sure be the explanation.

I'm starting to read schemas with succes
I love to know reasons why things work a certain way. EM's are fun, totally hooked