That must be a problem with the Chandlers machine.
Charlie was always very keen on the Plek. I believe he had the first one, when at Kew, and developed and beta tested it.
Lakland and Lull Plek all their basses. If those guys were getting variable results then they wouldn't be using the Plek process.
Having said that, the guys at the Gallery did a very good job when they leveled the frets and setup my bass the old fashioned way last year.