So my 980 still has the same old Collins Radar Altimeter that it had since it was new. It is interfaced so it no longer has an external display-- it just shows up on the G600, which is nice.
However, and this has been an issue with the airplane as long as I have had it, at cruise it sometimes starts to think there is ground beneath us, and will cycle up and down. It doesn't happen all the time, and I think I've finally figured out that it is related to cold temperatures-- it usually doesn't happen much in the summer.
Anyone else have this? At cruise, if it starts to do this, I just turn it off and turn it back on descending through FL180, when it seems to work fine.