Tom,
When in a Switch Test, it is okay to link the Column and Row wires together to eliminate the switch and diode, or to by-pass the diode if that's under suspicion.
A continuity test across the switch itself would show if it's making contact. There really isn't much in the construction (pun not intended) of the target to cause an unseen failure; a micro-switch can fail internally, but the contacts of a spot target are in the open.
In addition to the playfield parts page, look at the switch matrix and locations pages. That target is switch number 82, which indicates Column 8, Row 2. In switch test, check each of the other switches listed for Col. 8 and Row 2. It's quite likely that one of those lines has broken at another location, Col 8 seems to include a few spot targets, which are noted for it.
In fact, all but one of Column 8's switches are around that mid-left area, three targets and the two rollover wires leading to Blast Zone.