Well if you allow for perfect precision in the stone work they could hollow out the bottom of the plugs to allow placement of rollers and when at the bottom of the ascending passage fall into recesses in the floor that are unplugged in turn, that way the first two plugs could pass the later recesses.
Offset(side to side) rollers for front and back would allow the front rollers to bypass the recesses for the rear rollers. Say front rollers are to the outside of the plug while the rear are located towards the center of the plug, running along the length.
Of course no need for recesses to drop rollers in if the rollers were barely clearing the bottom of stones just apply some mortar to the area to be covered by stone and the excess would be pressured to the space and fill it in with the excess being squeezed out.

"What ifs" are fun for mental exercises.


Regards,
Lobo-hotei
lobo

Treat the earth well, It was not given to you by your parents, It was loaned to you by your children.
Native American Proverb