I have a tbs tango 2 TX connected to a diversity RX and tbs unify pro32 VTX.

when I run the lua script from the radio, it loads few of the settings for RX or VTX, then after a few seconds pause, it displays an error.

I wonder what is the cause and how to fix it?

Did you try the Agent Lite Lua? or the Crossfire Lua script?

Try and keep the quad a couple of meters away and plug in a lipo.