Kaput

If it still runs the motor and lights normally I'd lean towards the amplifier on the decoder being the issue. Contact Accurascale and they should see you right (probably send a replacement decoder, I'd suggest you consider removing the sugarcube speaker if they do).

The capital letter is important with the z21/Z21. The small z is the lower end starter version (and its white). The capital Z is the full function all singing all dancing version (and its black).

Worth noting the Z21 can update firmware/sound on most Zimo decoders. The z21 can't.

That might be a first that I've ever seen it said a 21MTC had more outputs and greater flexibility than a Plux22. Interesting. At least with Plux22 theres only one type.

Not read the decoder fully in a while but this is the swiss mapping for mine if its of any use:

Comparing with the function list for mine thats the first batch. Had a read at the PDF version of the sound documentation and it sounds like the first batch need to use a function to turn on the cab light but the 2nd batch has it on by default when stationary. Class-24-RTC-F-key-List.pdf

I think that post is referring to the newest batch of OO ones (which amusingly went from announcement to decorated samples in what seems like only a couple of months).

It feels like the new batch of N gauge 68's has got lost in transit somewhere, been in the coming soon advert in magazines multiple times.

I'd have to dig out the paperwork to confirm but I think the ability to manually turn off the cab lights was only added to the the second batch of 24's. F20 is supposed to turn them off on the RTC version at least, probably some sort of CV change doable to make it so they were off by default and F20 turned them on.

I'm not sure that one will work the cab lights, I had to change my Zimo MX634 into a "C" to get the correct logic level functions (the "D" version didn't work) for them. According to Zimo manual the C is logic level on FO3 and 4, I think the Rails Connect decoders are full power on all outputs.

What decoder?

Since I am one of the ones with an issue I'm failing to see how it's unhelpful. It's simple maths, you sell 1000. 500 never see much/any use. Means your only hearing feedback from half your sales Then there's the habit of modellers to just fix things themselves (and moan on YouTube about it) and the manufacturer hears nothing until said YouTube video I've only commented on it here and in messages to Accurascale support so I'm not getting involved in any conspiracy stuff about agendas. Ultimately I'm on my 4th one with a motor issue which if it wasn't for preferring the Accura version I'd have gave up and went Bachmann. Admittedly I never contacted them about number 3 because I wrongly interpreted them as having no support for second hand purchases. This has now been clarified hence awaiting new motor for number 4. Hopefully Accurascale can get to the bottom of the issues and we can all get back enjoying their products.

I wonder how many of the thousands sold have never been out the box or ran on a track and how much impact that has on the reported faults. Or even how many are used on shunting layouts where I don't think the motor surging issue would be as easily noticed. Just some idle thoughts while I wait for my new motor 🤔

I'd imagine its different because smaller coreless motor and speaker space.

Mine (BR Green 20002) does seem to have a few wheels not quite touching the ground but so far its had no derailing issues (code 100 settrack). Only thing i've really noticed is the bogies don't always look like they've re-centered after curves and the body was being bowed outwards a bit by the windows in the middle (filed them down but its not 100%, there really should have been a slot in the chassis molding for them). I'm going to assume the issues being mostly noticed on the green 20002 is simply down to it being the most popular.

After an initial reply that made me question if my email had even been read properly (asking for information I specifically provided) there should be a motor winging its way to me. Fingers crossed.

Doesn't really matter what Bachmann says, the controller determines whether a function is latching or not. For example on a Powercab all the numbered functions are latching and can't be changed. The separate horn/whistle button is a non latching version of F2.

After a bit of internal debate I've decided to contact Accurascale about getting a replacement motor...

Good news for those worried about the new decoder socket in these (and the 59). Zimo seem to have announced they are doing decoders for it on their website. Sound one is listed as "available soon" with non sound due Q2 2024

Don't suppose you have any pictures?

As annoying (and sometimes stupid) as it is, its perfectly normal that DPD wouldn't deal directly with you. Their contract is with Rails, Rails are the customer. Not you. Always a bit odd to hear of issues with DPD, they've almost always been my preferred courier. Edit: This post looks a little out of place now that the post I was replying to has vanished.

Oh well, after weeks of no issues my latest attempt at an Accura 37 is now doing the motor surging crap. Sigh.

Next18 ones that actually comply with the Next18S standard for size

They do seem to be one of the shops with a terrible stock system for their website. Stock status on the site doesn't seem to reflect reality and if you order something not in stock they seem quite happy to sit on your money until they get the item. Bit troublesome when they are also one of the shops still listing things that have been out of production for years and letting you order when there isn't a chance in hell of getting it.

The EFE Class 35 is just the original Heljan version so 8pin decoder and probably doesn't have any red lights. The HM7000 decoders don't support any sort of function remapping and I'm 99% sure they have F0 set as F0f and F0r so the lights should work in either direction. I do recall the older TTS decoders having random issues with lights only working properly if the model was sitting on the track in a specific direction with some controllers, what controller is being used here? And out of randomness, have you tried with the stayalive disconnected?