Having a unique issue I think

I moved from insteon which I may move back, I bought z-wave leak sensors before I knew there range limitations, picked up a z-wave switch wired it up stairs and connected, to sensors, could not connect had it replaced with same issue, my house is 900 sq about 25 feet to isy replaced it and wired in a honeywell switch, isy almost instantly recognized it and it would talk to the leak sensors, tried to add a second switch to improve the rf no chance the second switch which is 10 feet away will not add, tried a different brand, no luck. the honeywell which is closest seems to cut in and out non stop. I get interference, but nothing I have should interfere with signal, the honeywell populated just fine. Faster then any other device.   Either something is wrong with network or with isy but isy has been stable for years, Just amazing how the signal cuts in and out being 10 feet away from isy not their claimed 150 ft which is further then my whole house. I like z-wave but thinking of scraping it due to difficulty