RXV - On Deceleration Motor Break goes full on/off back and forth between 20-10 MPH

[Stazar]

Hey all - first time question asker. If I don't provide all the info needed i'll follower up with whatever is requested.

Cart: 2018 EZGO Electric RXV 48v Lifted top speed 20MPH

Symptom:
When I push the accelerator down and get going to full speed (or any medium to high speed) and then I let go of the accelerator after about 1 second the Motor break kicks in full and then after one second releases and lets the cart coast. Then after another second it kicks in full again and then after another second releases again. Back and forth until it gets to around 10 MPH. The result is all passengers being treated to necks snapping forward and a second later snapping back and that continuing over until one of the following happens:

If the cart gets under around 10MPH it stops happening. If I keep it under 10 MPH this does not happen. If I immediately switch my foot to the break and even lightly press it it does not happen. If I simply reduce my pressure on the accelerator to say 5% (so its still effectively coasting / slowing down) it does not happen. The key here is any pressure on the break or the accelerator stops the errant behavior. As does cruising at low speed.

Background
Bought this card from a horrible place in Palm Beach county called Beach Side Golfcarts 4 months ago. This has been going on for 3 of those months. They claimed they sold us the card with new batteries but in-fact they were 4 year old batteries and end of life. When we brought it back to them they sold us new batteries and told us that would fix the problem. It didn't. Then they sold us a new motor break. That didn't fix it. Then they replaced the solenoid. That didn't fix it. Then they returned the cart to me and said this is normal functionality. It obviously isn't.

We then took it to a new dealer who basically said they don't know what is wrong but that there are a lot of things about the cart that concern them and that what they want to do is rebuild the whole thing and put a new wiring harness in.
That will be
$1,500-$2,000 in labor
$1000 for the wiring harness
$2,500 minimum - and they don't even know if that will fix the problem because they say they don't know what the problem is.

My Questions For You All

1. Any thoughts on what this could be? I'd prefer to not have to pay all of that money if its something I can fix myself for a couple hundred.
2. How hard would it be to buy an OEM wiring harness and install it myself (I'm handy but minimal experience with this cart)
3. Is that a reasonable response from the dealer?

[Scott quail]

Try this first, pull the brake pedal back towards the seat and hold it back and try it again. Sometimes the spring gets weak and if the pedal moves slightly, the cart thinks the brake is being pressed. So try that first to rule out the simplest thing.

[usgicollector]

Someone could have gotten into the parameters Regen braking and made some very bad adjustments. It takes a person with some knowledge to set these right.

[Stazar]

Originally Posted by Scott quail

Try this first, pull the brake pedal back towards the seat and hold it back and try it again. Sometimes the spring gets weak and if the pedal moves slightly, the cart thinks the brake is being pressed. So try that first to rule out the simplest thing.

Tried this - didn't work

[Stazar]

Originally Posted by usgicollector

Someone could have gotten into the parameters Regen braking and made some very bad adjustments. It takes a person with some knowledge to set these right.

Ok i'll ask the dealer to take a look at this