From what I can remember V+ can record 2 channels while watching a 3rd so your issue is your first recording is 90 minutes so your second is 60 minutes you are then trying to add a 3rd + 4th recording while recording 1 & and 2 are still in play. Try using +1 channels for multiple recordings that way you can space them out better
Appreciating what praxis has said, what you are trying to do should work. The only time it has ever failed for me is if consecutive recordings are on the same channel. The V+ should simply dispense with any padding that has been set.
Cable customer since 1993. Services: FH TV, Sky Sports & Movies (2xV+), Talk Unlim Telco, VIVID 100, Virgin PAYG Mobile