Yes, that was my expectation that the MRF-300 would be an upgrade. Thanks for the sanity check.

The fact that address 0 is behaving better is probably an indication that there isn't RF interference, but something wrong inside the MRF-300 box itself. RF interference that occurs every 5 seconds or so should be readily apparent on either the antenna or the 300. But if the MRF itself is dropping or corrupting the data internally, it could randomly decide the data is meant for a different unit and cut off the flasher.

I suppose it's possible the unit might even be interferring with itself, such that when a lot of data is received is when it's most likely to corrupt or drop data.