I need to replace a dead router with something new and think the Netgear R7800 might be it. The 5 GHz wifi is very important to me because my apartment is in a large building with 100s of 2.4 GHz routers so the air is polluted with 2.4 GHz interference. I disable the 2.4 GHz transmitter and only use 5 GHz on my old router and will have to do it this way with a new one too. I read some comments about the R7800 and LEDE with 5 GHz as being unstable in the developers only forum. Is it true with the latest stable version?
It has been stable for me on 17.01.2, but like you I've seen some report instabilities with versions beyond that. I haven't tried .3 or .4 releases myself yet.
I have been using 17.01.4 for a few days and have no issues with it.