I will check (currently traveling out of town and will check as soon as I get back). I don’t think this issue should happen, because non-sequential stations do not participate in the calculation of start times.
A few things to check though: did you happen to set a Station Delay time? If so, that could explain why valve 2 is scheduled at 20:00 and not 10:00.
Another thing to check is whether this 20:00 has to do with valve 4’s run time. For example, if valve 4 is set to run for 30 minutes (or 15 minutes), does valve 2 start time change correspondingly to 30:00 or 15:00? If so, that means its start time is influenced by valve 4’s run time, and that will give more information for debugging.