Anyone has ever faced with their reverse just dont click/lock in place?
I have sent it back to the workshop apparently they couldn't seem to pinpoint after nearly 90% dismantling and swapping the related parts of the ATV.
However, from their findings which have been bugging them were, when they grounded the reverse sensor which located under the seat to the body; the reverse would work.
And when they directly connect the reverse cable instead to the display panel, the reverse would work, and so thus the reverse will not light up.
and the only time when the reverse work normally is when the gear is set to 4x4, other than that, it just went nuts.

the last thing that they have to do is now to dismantle the transmission box, which i dont think it will work.

I know there's speed delimiter, but from the manual it only said for forward, it didnt say for reverse.
in addition, whether i press it or not, it seems it is not working.
any ideas?

When you put it in reverse the sensor opens and the ind. Lights up. When this happens the machine limits the rpms. By grounding the wire lead you bypass the Rev limiter but no light. The shifter should have a detent ball of some sort. At the shifter lever or drum or both. I have not dug into this model so I can't speak  to where it is. Maybe one of the other members might chime in on this.

Ok I  looked at the service manual. On 6-11 of the cf-500-5b manual available here on the forum. shows the gear position bolt. This holds the spring and detent ball. It also shows in the picture the reverse sensor. It looks like the older style sensor. They offered a updated part. See my z6 issues tread for part number. To check the detent, disconnect the shift rod from the engine side. You will be able to turn the lever and see if it clicks into position. If it does than look at the shifter lever assembly and check the detent on it. If all ok you just need an adjustment. If the lever on the engine does not click than pull the bolt out and check the spring behind the ball and make sure it is not weak or broken. Let me know how it goes.