The function is stable but the radio you are using does not offer the necessary commands to support that function in XCTU. The fact that you had it partially work was it polling a few of the commands that the Digi Mesh 2.4 module supports. But it will not support it fully till the reset of the commands are added to the 2.4 Digi Mesh code/module.
Yes you can achieve a mesh. will it work on the 3rd party code you have? I can’t answer. You need to look into the interface they use with that code and check the manual to see if it matches. If it does, than it should work.