Do you have your schedule set so that both controllers may end up running at the same time?
The issue may be that when one controller is active (#2), the second controller is completely disconnected from the load.
Try hooking up one of your new relays as a dummy load to terminals 1 and 4 of the left relay within your old munro smart box. Please note that the relay should not have any load attached, meaning that terminals 2 and 4 (or 5) of the new relay should not have anything attached on the new relay.