I have a feeling we are talking about several different things here. 9.26.01 version had an problem with creating 7zip files, which was not in relation with any other bug.
Whole 9.xx>9.26 7zip support has issues with some specific 7zip files in a way that it could not read it but it could be read by 7zip FM. Complete code was changed in 9.5 release so this problem does not exist anymore, in >9.5 releases.
Anything else is an separate problem needing its own thread. If files “dissapear” from 7zip archive, and can not be read by 7zip FM, then this would not be PA specific issue. I do have to say that nobody reported anything similar to this so far.
So, for best 7zip experience, or rather for best PA experience, use PA 2006 9.5, as with every other PA release, not only it has more features, it is also considerably faster.
thanks, closing this tread!