Trying to replace an older mx350 non functioning remote with a new mx980. The RF seems to be very spotty regardless of channels. I've never used a mrf250 base but seems very similar to current models. Is there a known frequency issue between Newer and older gear?

It's gotta be that mrf250.

You could move an emitter wire 1" and the thing wouldn't work at all. Very susceptible to interference.

What components are responding unreliably? Certain components are unreliable, regardless of RF brain (ATT cable boxes come to mind).

With that said, throwing the MRF250 in the trash and replacing it with an MRF350 (not an MRF260) will probably do wonders. URC still hasn't admitted it but I think they changed something in the MRF260 about 3ish years ago. Before that, we RARELY had issues with them. We then ran into a number of problems all with MRF260s. In every one of these jobs, we replaced them with MRF350s and everything worked fine.

+1 for Punter's comment. Haven't had a successful MRF260 install in years, we only spec the 350 now too; and even its reliability/susceptibility to interference has gone up significantly in the last 18 months.

Well, interference has also probably increased in the last 18 months. Several people have complained here that HDMI cabling near the MRF350 has caused spotty performance. Good ol' HDMI.

I ran into the HDMI thing recently.

After converting from Component to HDMI the MRF350 wouldn't work at all.