[2019] Staff on Stryke Achievement Bug

Hello men goodest of days,

I can't complete this achievement:

"Kill a Desert strykewyrm wearing a full slayer helmet and wielding an ancient staff."

I've tried a lot of things. Restarting client, using normals and ancient spellbooks (even though it says ancients are no longer required for it), using every sort of slayer helmet (normal, full, reinforced, strong, and mighty). I've tried only equipping the Ancient Staff and Slayer helmet, and while also wearing other items. Both Legacy and EOC has been tried but gave nothing.

I've tried killing them off-task and on-task, with the desert strykewyrm mask (which makes me unable to attack them at all) and with the normal slayer helmet

Nothing is doing the work.

Fix pls