HT-M02 V2 OS update

We had well working HT-M02, LTE and chirpstack v4, whole package. Then I saw a new version of the OS in Heltec’s pages and decided to install it. After that we have not been able to get LTE working. EC25 connects fine with ISP, but the communication link is serial. In former version in /dev was a cdc_wdm0 connection. The cdc_wdm driver is in drivers but it will not be loaded. I could not find any instructions in the web. Does anyone know, how to repair this. One possibility could be if I could get the former/original OS back. Can I download it from somewhere?

Downloading a new OS version is not so straightforward. First all went quite well but in trying to find the cdc_wdm connection I installed the OS some 4 times. Every time erasing the flash was more difficult. I had to make it in increments, typically 11, 63, 89, 100 % at a time. Also downloading the image did not work every time, maybe 1/3. Is there a limit, how many times OS can be downloaded into the flash.