Interference with two Zwave Primaries (Vizia RF+ & Smartthings)?

I have expanded my Smartthings network with Hub v. 2 and more devices. I have had for several years a Vizia RF+ system working just fine. Both are Primary Z-wave networks that share the same space. I have some Leviton devices (both Z-wave and Vizia RF +) on the Smartthings network. I use the dongle on my laptop with the last release of the Leviton software.

I am experiencing problems, delays etc. on the Vizia network. One of my controllers died - could not reset. The programming software instead of showing the mesh network now says “portable” for all of the mesh connections.

Do these two networks stay separate or do they share the same mesh nodes regardless of the which network they are attached to? Are there other interference problems between these two z-wave networks? Some of my devices on Smartthings seem to be working ok including the zigby sensors.

I have a version 1 Smartthings bub for a couple of years with only my smoke detector paired and it worked fine. This problem has only come up with the Version 2 hub and the addition of more nodes to it.