ME22N (and other, similarly complex transactions using Enjoy controls) are quite challenging when it comes to creating Personas flavors. A lot of objects have embedded elements which themselves consist of multiple embedded elements as well, and so on - which then can cause issues.
I'm not sure about the exact reason for the problems you are experiencing, but in general, you should try to avoid changing the size of the scrollable and collapsible containers or be very careful when relocating containers. According to my experience, such actions can easily cause certain functions not to work correctly, including proper collapsing and extending containers.
Playing around with ungrouping such embedded controls may help too, but it has to be tried to see the result.
The Step * script error is almost certainly caused by some issue with tab caching / merging. Due to the actions behind the scenes that are happening because of caching, a control that you'd think is available is not seen by the flavor. It is likely that you'll have to revisit your flavor design to get around the problem.
Sorry to be vague but finding the culprit requires to look directly at the situation and it's not possible to give the exact reason remotely.
Also, you mentioned that you have all the latest notes applied. Does this also include the very latest Personas client version (059) which came out last Thursday (9th of October)? Just asking because it has been discovered that there is a problem in this patch with hiding elements and still accessing them via script, so I suspect that this may have some role here.
If so, then you'll have to revert to the earlier client version (036).
Development support is aware of the problem already.