The openPDC would not be able to decode the data frames unless it receives a configuration frame that is not malformed. Based on your screenshot, it seems that the openPDC is receiving both CFG1 and CFG2 in addition to the malformed CFG3 frame which is unusual in my experience. But that probably explains why the malformed frame doesn’t have any impact on your output stream. openPDC is able to decode the data frames coming from the PMU because it is receiving the configuration data it needs from the CFG2 frame.
In terms of impact, this means that openPDC will not be using the information provided by the CFG3 frame at all, because it cannot be decoded. I suspect that you could turn off the CFG3 frame in the PMU and everything would likely work the same as it currently does. If your process does not rely on any data from the PMU that is exclusive to the CFG3 format–such as long station names or long channel names–then this error shouldn’t have any impact at all.