I think I was following ok until here
there is one sub report that the volume is counted by simply counting the records in the queried record set,
If you're saying the sub report that is the 'foundation' for the rest can have no records? Then what about cancelling the main report opening?
Assuming all the sub report properties are correct (grow/shrink/report view, whatever) maybe you have an issue with the report reformatting itself when you switch views - or are you not switching, but rather closing and opening with a different view? I read about the situation before - seems the issue was the sub report queries could not process fast enough, so the solution was to migrate the data to a temp table and open the reports from there. Also, I believe sub reports load before the main opens, so maybe the order of the loading is not conducive to the relationships you've made between them. If you have not tried, perhaps opening the subs in print preview on their own (I guess you'd have to fudge some data that they'd be looking for) and see if a) they open OK, and b) if they have records. That's all I can think of.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.