All inspection switches have an “on” input and an off (monitor) input. You get invalid inspection IO when both are in the same state, usually both off.
Car top inspection INCT (on car top inspection) & INCTM (off)
In car access INHA (on access) INHAM (off access)
Machine room inspect INCN (on) INCNM (off)
Then there are monitors on both door bypass switches that’ll give you this fault too but I don’t recall their names off the top of my head.