I just hit this for the first time trying to buy a ticket using an eCredit on the mobile web site. Switched to the Android app, saw the eCredit still had the full amount, so went through the process again and upon clicking purchase got "Your session has timed out", muttered a curse and thought I'd have to try a 3rd time but noticed the amount of the ticket had been deducted from the eCredit and indeed the reservation had gone through.

Then called to apply RUC since it had shown space available at booking and got through with basically zero hold time (around noon Pacific today)