I called for Climb Thrust in a B767-300 years ago out of Hong Kong at night at MAUW and exactly that
Sticky thrust lever, auto throttle reduces thrust for level-off, one comes back, the other stays put
happened.
It got my attention, I quickly checked the screens and pushed the errant thrust lever back where it should have been and all was well. Back in those days I didn't keep my hand on the thrust levers but quess what, now I do, every time they are moving. It also became company policy some years later.
As an aside, one reason I like having moving thrust levers is that it makes it a little easier to monitor the performance of both the autopilot and the guy sitting next to you.
Regards,
BH.