I like to post comments that clarify issues raised in past posts. This comment was posted by a crew member that pulled alerts in the 1990s and was a reply to my post,
I was at Tango-0 in the early 90s when one of my sorties had similar indications (except no missile away/MV400). It ended up being a bad DCU/MGS. After a series of Radio out and Cable out indications, and target change indications (erroneous because TVR/TOTR did not validate) it finally dropped LFDN, then came back and then went ASG. It was a dying Digital Control Unit in the MGS. By the way, it's called a Ground System Test (GST), not SCN test in Deuce.
The above comment shows that malfunctions did occur out in the field. Sometimes these malfunctions elicited strange indications. I appreciate that the commentator provided a clarification for GST vs SCN. This being one of the many differences between MM II and MM III.
Notice that one does not need the presence of a "UFO" to cause these strange indications...a dying/malfunctioning missile guidance system will do the job quite nicely.