Go to Photo #8 in the link below. It illustrates what this video is saying. Apparently the wind pattern (venturi?) between the Allegro and NML causes rain to go up into the vent as indicated by what appears to be moisture on the right and see the residue of water on the bottom as it streamed toward the camera. Photos: paulkurodastore.com/nml205ventleak/
The wear groove in question is on the right hand U-channel just below the gib (guild) traveling in the first scene.
For comparison (at 1:00) I shot south doors' leading gib in channel without any wear issues. Then more of the door in question.
See how gibs' mounts, closeups of various ones: paulkurodastore.com/nmlelevatordoors/
To view the main infrastructure of this system, pause at around 6:18. It the shiny metal horizontal structure with black square in the center at the northwest inside corner of the 2nd street building (right of the video frame). In this installation the lines crisscross corner to corner. For ours, it will be diamond shaped because of the water tower structure in the way. Video actually ends at 14:08 where it is advised that catenary is the best method for our building because of the patios. Also we had Scaffolding, Inspection and Testing gave us an evaluation.