Device Slowing Moving Offline

I’ve had my ST setup for quite a while, started off with v1, and then migrated to v2 several years ago. Over the last few months, I’ve been having more and more of my Zwave devices go offline.

Some of them continue to be able to be controlled, but aren’t reporting status, so they work through the Echo, or App but just don’t report.

Sometimes, I can go in an replace device w/ the same device and everything works, other times it just gets hung at replacing device. It says… “The hub is not responding.”

I haven’t really changed anything, and a few of my devices are within 10 feet of my hub. I’ve reduced down to about 85 devices when i migrated to v2, but any ideas on what is going on. Or any troubleshooting ideas?