The choreography and musical interpretation held together but the total effect was diminished by little lapses in technical precision. (Should this be reflected in the second mark/PCS?)
There's nothing official in any of the PCS guidelines about reflecting errors in the PCS.
Skating Skills includes "Cleanness and sureness of deep edges, steps, and turns." Performance includes "Clarity of movement" (defined in the Program component explanations document from a few years ago as ""refined lines of the body and limbs, as well as the precise execution of any movement").
If you consider bad landings as representing unclean/unsure edges or imprecise execution of the movement, then you could reflect that in the appropriate component scores. E.g., "I would have awarded 8.5 for a clean performance, but each bad landing made a small blemish on the overall effect, so I'll only give it 8.25 or 8.0." (or whatever numerical values you would start with or adjust to)