Nested drop-downs (3) spontaneously corrupting

I have a project done in Robohelp X5 which worked fine. One topic is incredibly dense (very complicated procedure) and includes a three-layer nested drop-down text area (layer one contains several drop-downs, and each of those contain some as well).

Converted the project to Robohelp 7, seemed to convert okay. Did a spelling/grammar check on the printed documentation and discovered this topic was corrupted. The first layer contained the *links* to the second layers, but the *contents* of the second layers had migrated up into the first layer.

I rebuilt the topic (well, part of it), drilling down into the third layer. When I saved the topic I fell back out to the main view of the topic (as expected). Opened the drop-down text area for the first layer and... it had corrupted again.

Has anybody experienced anything like this? Any suggestions on what to do? Colour me confused for now :-(

Thanks!