Engineer Challenge 3 bug 920/100

After multiple attempts and countless different weapon systems and tanks used and lasers to include the Bradley and Recon laser, The Engineer Challenger 3: Deal damage to Laser Deignated enemy vehicles using lock-on weapons, is glitch/stuck at 920/1000 points and Ive repeatedly tried to complete the task. Ive found others with the same problem and attempted to untrack and retack the challenge but nothing has fixed it.