I remember watching this movie when I was a kid but it's only a few images that I remember. The droids in the movie were child-sized and just had "neutral mask" faces. Anyway, the biggest image is of two identical droids fighting in an enclosed space (like the back of a truck) and that the bad one drilled a hole in the good ones face. Later, this helped identify the good one because of the "birthmark".
On the remote mining planet Ordessa, the management uses killer military police androids to crack down on workers upset with the terrible conditions. Lorca (John Tarrant) and his mother Abbie (Donogh Rees) led the human underground resistance movement until Abbie was killed by androids. Now, Lorca and Suzi (Cassandra Webb) battle Captain Jowitt (Ralph Cotterill) and the brutal bounty hunter Danny (Hugh Keays-Byrne), with the help of the friendly android Grid (Deep Roy).
This review mentions the drill mark.
Abbie fights on after the crackdown, making life miserable for Jowitt by packing robots full of explosives and programming them to visit the maintenance facilities. Grid is unfortunate enough to be nearby when one such walking bomb goes off. The arriving response team of droids hauls the poor little guy in for questioning, probably due to his wearing a "Members Only" jacket (makes you look guilty). Before releasing Grid, they bore a hole in his forehead with a power drill. Reminds me of the way researchers mark rhinos for easy identification. They would tranquilize the beasts, then cut wedges out of their ears. Sometimes being an endangered species sucks.
I remembered it from the prior time this question came up, at which time I watched a version online, since taken down. Your description is accurate.