After onwning my Somment for a month I had this issue and it got worse and worse from once on a ride to around 20 times in a three hour ride. Sometimes when I got the E020 code the bike would not turn on again the Shimano startup displayed then turned off again and I had to ride in heavy manual mode 
At one point the motor would not turn on or charge and simply leaning the bike slightly the other way it all started working.
I found whoever had built the Vitus Sommet at Chain Reaction had stuffed the wires for computer and remote switch in behind the motor cover, forced it closed and half stripped a screw. The cables had been heavily compressed against the frame and were indented significantly.
Spoke to Chain Reaction and they were happy to replace but I needed to get a LBS mechanical to provide a diagnostic report and an estimate. Grrr. Why photos are not enough on a month old bike is a puzzle.
Anyway later - when adding a light and removing bottom battery mount I noticed it was on the bottom of the sliders. I adjusted these back up about half way (just a guess).
When putting everything back and re-inserting the battery I now see that the release now falls onto the spring holder - previously it just fell out.
Motor has now been working fine since (two rides) and no E020 codes. So this was caused by the battery moving due to mount placement (must have moved down when in use over the month). It was not obvious as the battery didn't seem to move I think because the top lock works so well and I suspect you might also be able to adjust the top mount - but I have not tried this.
As the Shimano EP8 installation manual says the distance between mounts and alignment is critical and just in case (because I read of other peoples issues), I have been checking the battery just after rides to check if it is still retained the same and if the terminals are getting hot, it has been fine and terminals have been normal.
Hope this helps anyone else who gets an E020 error code but I do think this could be displayed for many reasons.
At one point the motor would not turn on or charge and simply leaning the bike slightly the other way it all started working.
I found whoever had built the Vitus Sommet at Chain Reaction had stuffed the wires for computer and remote switch in behind the motor cover, forced it closed and half stripped a screw. The cables had been heavily compressed against the frame and were indented significantly.
Spoke to Chain Reaction and they were happy to replace but I needed to get a LBS mechanical to provide a diagnostic report and an estimate. Grrr. Why photos are not enough on a month old bike is a puzzle.
Anyway later - when adding a light and removing bottom battery mount I noticed it was on the bottom of the sliders. I adjusted these back up about half way (just a guess).
When putting everything back and re-inserting the battery I now see that the release now falls onto the spring holder - previously it just fell out.
Motor has now been working fine since (two rides) and no E020 codes. So this was caused by the battery moving due to mount placement (must have moved down when in use over the month). It was not obvious as the battery didn't seem to move I think because the top lock works so well and I suspect you might also be able to adjust the top mount - but I have not tried this.
As the Shimano EP8 installation manual says the distance between mounts and alignment is critical and just in case (because I read of other peoples issues), I have been checking the battery just after rides to check if it is still retained the same and if the terminals are getting hot, it has been fine and terminals have been normal.
Hope this helps anyone else who gets an E020 error code but I do think this could be displayed for many reasons.
