Not working on Raspberry Pi

[static75]

I'm trying your code on Raspberry Pi, using Python 3.7.3, and I have a USB-to-DMX cable connected to ttyUSB0. I know the cable works because I used it with my laptop and Freestyler to control my light ADJ light fixture (6 channels). When I run the code, my light fixture knows that something was transmitted (it rotates to an odd pan/tilt position and the light turns off), but it doesn't seem to recognize the actual channel values.

In addition, I added a "print" function in your DmxPy.py file to see exactly what was being sent to the USB port for DMXOPEN, DMXINTENSITY, sdata, and DMXCLOSE. If I send six channels with values 1 thru 6 accordingly, it seems to transmit correctly. b'\x00\x01\x02\x03\x04\x05\x06\x00...

However, if I set channel 1 = 127, channel 2 = 127, 3=8, 4=1, 5=10, and 6 = 6, the byte stream seems to get corrupted.
b'\x00\x7f\x7f\x08\x02\n\x06\x00...

Am I doing somthing wrong to run this code? Am I missing a step?