does anyone know about this error?

I haven't experienced the error myself yet, but it sounds like there is a problem in one of the files. Try to re-extract the netlist. Make sure you have enough free diskspace ("df"). Check the file contents with an editor.

Sounds like an issue with the spice netlist. Maybe this is unrelated, but the "out" pin in the schematic is actually using a in-out pin symbol. Are you simulating the spice netlist of the testbench or the inverter schematic?

this I'm just testing for the Invertor schematic.