Several owners reported motor surges, which is almost certainly a controller fault.
Very unimpressive, given that it's basic hub motor control technology which has been in use for 10 or 15 years.
The faults were on earlier bikes, so may - or may not - have been sorted by now.
I had one of the first Brompton Electric bikes. The motor was “clonking”, kept surging and often cut out completely... I then had to switch off and back on to reset the system.
The bike went back to the factory where, I’m lead to believe, had a new motor and controller. The result was.... it was worse than before.
I got a full refund.
I waited six or so months for things to settle down and tried again. It was alot better but occasionally cut out after a “freewheeling session”.
The main problem I have to say is the motor surge on startup. This got me thrown off the bike twice with wheel spin. I’d had enough so reverted to a non electric version for the car boot and a Cube Compact Hybrid 20 for longer trips on very hilly terrain.
I was told by Brompton never to change power when riding. The reason was “it will upset the bike sir!” So if you ride on undulating roads and need to change power level you have to stop, press a button on the battery, then restart. Brompton need to add a handlebar controller for adjusting the power.
Enough was enough so I sold it..... as with all Bromptons I got a great price for it.