VESC Tool cannot connect to VESC

Hi VESC Community

I am new to VESCs and really excited about them. To start playing around I bought two flipsky 4.20 vescs. I modifyied conf_general.h in the firmware to use the hardware version 410. I have uploaded the firmware through a st-link and it seems to be working just fine for one of the ESCs. The other one does not show up as a usb device anymore after uploading the custom firmware (I used the current master, commit 3a071ce). I observe, that after powering both vescs the green led starts glowing for the healthy VESC, whereas the malfunctioning VESC only shows the blue led and approx. every 2 seconds it shows the green LED very weakly and briefly.

There doesn't seem to be a short or anything like that, since my bench power supply is showing 0.02 A at 22.8V input.

Does anyone have an idea what could be going wrong? The VESCs are brandnew and it was used once this morning to test wether its working. Then I uploaded my own firmware and... ... nothing.

Some more info:

• working with ubuntu 18.04
• lsusb or dmesg | grep usb show nothing when connecting the malfunctioning VESC to the computer
• upload through the st-link with SWD port still works

Thanks in advance for your help.

Best regards,

Ecuashungo