I have a VEMS unit here (latest firmware) and same issues
If you can roll back to the previously working firmware then you should be fine. The problem is that there are about over 20 different firmware versions with VEMS! I supported the extra bytes for the unit requested in the later Nistune versions.
There are protocol changes with many different VEMS firmware versions and I've so far worked out the following changes:
Version 0.20, 0.33, 0.4.0, 0.4.1, 0.4.2
34 bytes (+boost)
Version 0.46, 0.50, 0.51, 1.42, 1.43, 1.45, 1.46, 1.47, 1.50, 1.51
37 bytes (+PWM, analog2)
Version 0.52, 1.52
39 bytes [+PWM int]
Version 0.53, 0.54, 1.53, 1.54
This was after going through the INI file for each firmware version and looking at the protocol table for the round unit and looking at the table
Current test versions of the software support the 32 and 34 byte VEMS release. Use a firmware version listed against those versions. I'll add support for the other ones soon
From this I need to work out the version number from the VEMS and then make Nistune adapt to read the correct number of bytes. Its a pain.
I've emailed VEMS with come technical questions about retrieving the version info last month (9 Sep) but nothing has been responded to yet.