Hi fellows,
I have a strange problem with ebike controller using STM32 uC (Device 
family :STM32F10xx Low-density)

I have a fischer 1606 ebike with a Lishui controller which did not have 
original display. I found that this controller has alternative firmware 
made by colleague stancecoke from endless sphere and formerly 
pedelecforum.de. Link to github with FW - 
https://github.com/EBiCS/EBiCS_Firmware/tree/cbbee7ec449f21d52dbe661d53a394d5e81c589d

It has several branches, master is for motors with hall sensors, there 
is also a sensorless branch that I am using, since fischer 1606 has 
sensorless geared motor.

So far I am playing with this controller on my desk, with only display 
connected using bench power supply (Riden 6030). Long story short is 
that sensorless version flashed to my controller sometimes start without 
an issue, sometimes right after start gets stuck in Error Handler. It 
looks to be input voltage dependent. At 48.6V, every power cycle ends up 
with E30 on my display (E30 is communication error, which is a result of 
program being stuck at error handler). If I change voltage to 42-43V it 
starts without problem most of the times. I tested also on battery to 
eliminate voltage ripples etc. and the same story.

I flashed master version and it works flawlessly regardless of voltage, 
but this is no use for me since I do not have sensors :)

I was asking stancecoke for help here 
https://endless-sphere.com/sphere/threads/lishui-open-source-firmware-project-kingmeter-5s.106862/page-17 
and he pointed this forum as a last resort :)

I am perplexed now, stance thought that it might be due to a bit 
"primitive" display handling and he updated it - no change, he asked me 
to grab communication between controoler and the display during problem 
and controller is mute, he suggested it might be some issue with 
interruptions, which I adjusted but also to no avail.
The stupid thing is that if I hook up to the board using Eclipse with 
disabled reset upon connection and also disabled breakpoint in main I 
can see it being stuck in Error Handler, once I press resume, program 
resumes, E30 disappears and the controller is working normally without 
any problems.

I am totally puzzled and do not know what to do further. There are some 
differences in branches (master compared to sensorless), like (and not 
limited to) ADC being handled by different timers and different 
frequencies.
Could I get some advise from you why it starts up normally at certain 
voltages while with others not? :)