Spear not locking on bot Fabs?

Just did a few missions on Vog-Sojoth, thought the free Spear strategem would help clear out bot fabs - but it doesn't seem to be locking onto them anymore? It locks onto other targets - dropships, gunships, hulks, cannon turrets, tanks etc. just fine - but it will literally lock onto a bot MG emplacement and completely ignore the fab right next to it. Anyone else experiencing this issue? Is it just with the "free" Spear strategem?