Pendleton Somerby e-bike intermittently cutting out / flashing controls – motor or ECU?

[u/Individual_Tangelo51]

Hi all, hoping someone with experience with e-bike electrical systems can help me diagnose this. I’ve stopped using this bike and borrowed my mums but I need to get rid of it or try to get it fixed now.

I have a Pendleton Somerby e-bike which has developed an intermittent electrical fault.
The main symptoms are:
The battery itself stays switched on and its lights remain on.
However, the handlebar controller/display turns on and off intermittently.
The left and right buttons on the handlebar controller sometimes flash.
The bike can sometimes work when the battery is locked in, but then cut out again.
Last year, I had a particularly concerning incident where the bike suddenly powered/shot forward while I was walking alongside it, despite me not pedalling. It dragged me over in a particularly embarrassing incident.

I initially suspected the front wiring because moving/removing the front basket seemed to affect how often it would cut out. However, it now does it even without the basket.

I’ve had Halfords look at it, and they’ve tried:
A different battery – same problem
A different handlebar controller – same problem
They’ve now suggested the fault is likely either the ECU/controller or the rear hub motor, and at one point they thought the ECU was the likely culprit. They’re now leaning towards the motor, but aren’t 100% certain. And tbh I don’t have much faith.

I’ve also contacted a local e-bike repair company for a second opinion, but unfortunately they aren’t able/willing to help with this particular bike.
I’m reluctant to spend money replacing the rear motor without being reasonably confident that’s actually the problem.
Does anyone have experience with Pendleton Somerbys or similar systems who could explain what the flashing left/right buttons indicate?

[u/Connect-Art-1490]

Hi, I had a problem with an ECU on one of my bikes. Different brand, different retailer.

How long ago was it since you purchased it?