i've never heard this documented elsewhere, most internet sources claim that DXM+THC is supposed to be pleasant, but definitely not for me based off personal anecdotal experience. (i've only smoked on the comedown, never during the trip)
this always happens if i am impatient enough to smoke a joint too early before the DXM high is fully completely over. even if i've convinced myself i feel relatively sober enough, no matter how minor i think the afterglow has became, the moment i have any weed before it's fully over my entire consciousness feels unpleasantly robotic. i'd describe it as a very overwhelming and uncomfortable form of dissociation, maybe. kind of like the DXM is re-activated if that makes sense, but in a bad way. it would last for days and days, not just for the duration of the weed high. but CBD always aided in killing it prematurely, especially in the latter stages.