"Deal damage to Laser Designated enemy vehicles using lock-on weapons"

Well this challenge has another layer of problem in it than just needing a recon using SOFLAM. the challenge itself is bugged, here is the only that was found to make it count : 

DEAD AIR : "damage laser painted vehicle with a lock-on launcher" : this one works only when these weird conditions are met : 
- you need to use the defaut "combat engineer" loadout , if this loadout is modified it doesn't work 
- you need to use the stinger as launcher
- the targets must be laser painted by the SOFLAM of the recon, any other laser tagging don't work 
- this challenge only count when you are on the map MIRAK in conquest mode