z9962 was accurate. In the section expert, select the group 1 section (not the group1a or group1b) and set the 'keep section together' as true. This will
try to keep all of group1 headers on the same page. If the combination of these headers is too large to fit on a page at all it will ignore the rule. It is only applying the keep togther to the header sections, not the entire group. That is handled in the group expert.
Another trick if the headers do not grow,
1. create another group header 1a (move the existing ones to b and c)
2. make its height as large as the other two combined
3. set it to keep together =true
4. set it to 'underlay following sections' = true