Can you clarify a few points, you initially said a PLC is being used, then described the modem as a PLM. Also in the description of the parts of the message you indicate “from my EZIO 017Fb3 to my plm 13AC0F” an EZIO2X4 address of 017Fb3 but the trace shows a FROM address of “01 7F 83”.
They look like garbage messages that my PLC sometimes generates unrelated to any specific device type (if you are using a PLC). If these are coming from a PLM they are very strange. The flag byte of 76 is a Group Cleanup Direct ACK of an Extended message. Since Group messages are not being used nor are Extended messages this is another indication of a garbage message. Also the command is garbage. A Flag byte of 30 in the second example is an ACK but of an Extended message which is not in play here. Also the command is garbage.
Please post the clarifications to the first two questions (PLC versus PLM and EZIO2X4 Insteon address).