Thought I'd give an update. Reducing the size of the chain seems to have fixed it. But will ride over the next 2 weeks and then provide an update. Haven't changed the stock chain ring. Still feels offset to middle gear would improve, and so still might try lekkie at some point. Will update in a couple of weeks.
Thanks for help.
A couple of other things I've noticed. Got a couple of error codes the other day...and at the same time the battery indicator kept changing levels ... hasn't repeated (someone suggested cold weather), but one thing I have noticed is the bars on the battery display, on the tongsheng display, don't seem consistent ... one minute its 3 bars and the next back up to 4. Perhaps firmware trying to be too smart?
Other thoughts over my Haibike:
1. Having flexibility over battery/ frame is great.
2. Power is not light and day, but its definitely more, and its nice to be able to remove speed limit. I've for the 54v/ 750w unit....and battery is ~725 Wh.
3. Its not quite as refined as my yamaha .... setting off is slower, to bring power on, and sometimes I feel the power assist drops off even on high assist, when I am not pushing, whereas Yamaha seems to have priority to movement first torque second.
4. Motor is noisier, but heyho.
5. Ability to service motor is again a big plus.
Upgrades (shortterm) being considered:
1. Bigger rotors....will eventually replace brakes
2. Change Tongsheng crank arms for Bafang straight to prove Q factor.
3. Tires ... and wheels ... bought a cheap bike and the current are cheap cheap.
Medium term I will look at the open source firmware.
Longer term better front fork.
For now I want to test reliability, battery life, waterproofing, chain issue (making sure its fixed), wear-tear and maintenance ... if all goes well, I will be selling my Hiabike (done 7000 kms and battery only gets to ~75% capacity) in the next 6 months.