What level is the firmware in the EZIO2X4? How often do you poll the EZIO2X4? Do you know the firmware level of the PLM? This information may be useful to SHN.
Until someone else has other suggestions or ideas, I would move the EZIO2X4 near the PLM plug point. You do not need to move the controlling circuitry. This should reduce the possibility of a truly garbage message. With the messages having inconsistent data (flags, cmd1, cmd2) they look like something on the powerlIne is trashing the message. Harder to happen with an Insteon message due to the CRC character but it does happen. I have 3 EZIO2X4s installed running v25 firmware for more than a year and have never seen those types of messages being generated by the EZIO2X4. Two of the EZIO2X4s are in a detached garage several hundred feet from the house. However, I do not poll the devices on a regular basis.
I’ll set up a test where I poll both EZIO2X4s in the garage and see if I can reproduce what you are seeing. Let me know how often you poll and I will use the same interval.