There's certainly security issues with the elections, clear problems with unauthorized voting, tallies that make no sense, and the possibility that the outcome in a state could be compromised by computer.
Consolidating the election into a singe system means a single point of failure. You could easily have multiple, overlapping intrusions skewing the results and those intrusion could come from both internal and external actors.
"Those who cast the votes decide nothing. Those who count the votes decide everything."