I'd guess your assumption is correct.
First thing first, I'd suggest keeping a neutral cervical posture while lifting, ie. head in line with spine, not looking parallel to the ground or (even worse) up.
Get off the nightshades, if you aren't already.
Maybe check to see if this happens only on one style of DLs (ie. "normal" or sumo). There could be a difference due to the change in angle of the arms in relation to the torso and the torso-to-ground angle.
With plates and screws already in place, unless it is remedied some other way, I'd say early on that ditching DLs would be a small price to pay.