Not sure how that was achieved, but perhaps setting the unmanned property to 'true' for this UFO would be better. It would even allow you to change the UFO health to another value more befitting a drednaught. Altho I guess the shield value is there to offset this low HP.
While I'm at it, UFOs:
- STR_SABOTEUR, and
- STR_MIB_ESCORT_SHIP
have an 'invalid' size, STR_MEDIUM, should be STR_MEDIUM_UC.