Prestocard "undercharge" & duplicate payments

My struggles with the transit system continue. My card is currently locked because they disagree with the way I've been using it.

They call this an "undercharge", meaning they think I tried using the card without paying. So I logged into the online lookup for my account to see what history could teach me. There I noticed that several of the charges appeared more than once. As it currently stands, I've been overcharged $19.01. And that's in just three weeks. I guess it's up to Prestocard users to be vigilent about the balance on their card and what they're being charged by Metrolink and the local bus companies.