I just had a play:-
For info: there are two episodes of The Apprentice USA on BBC ONE Sunday night (2335 and 0020). They carry different P-CRIDs and the same S-CRID.
On the SUI: Set the first episode for series record, and all is well (both episodes are marked as set for recording). But, set the second episode and the first episode is not marked as set despite a reboot. However, having rebooted, setting the second episode also marks the first! (unit 1)
On the WebIF: Setting the second episode only marks the second episode (even after reboot, and even as reported by the SUI). Setting the first episode marks both episodes. (unit 1)
On RS: before sync, setting the second episode only marked the second episode as pending; setting the first episode only marked the first episode as pending. After sync, with the first episode pending both became marked as set (unit 2), with the second episode pending only the second episode became marked (unit 3).
I suspect that, nevertheless, both episodes will record. I will leave these settings in place and report back what actually happens (I don't care whether they record or not).
The only observation which breaks the general pattern is what happened after a reboot, when the SUI started working properly, consistently. Note I have not rebooted units 2 or 3.
My hypothesis is that (when working properly) the SUI maintains a database of series linked episodes and sets all the items in the list when you set any of them (which had failed before I rebooted), but maybe WebIF/RS doesn't look for episodes that occur earlier than the specific one you set. If so, I'm surprised nobody has spotted this before. If not: I have no idea how the SUI can mark the first episode to record by setting the second episode, but the WebIF and RS do something different.
Questions (for somebody else to have a play): Are my observations repeatable? Does this only apply to The Apprentice USA - are there other examples of multiple episodes, and do they work properly or show the same effect?