Been reading the DAZ Carrara forum and it appears 8.5 is far from working! My version can't load a lot of content that the previous version had no problem with. Tends to be none DAZ Original content, which makes sense since unless the developer(s) update their products they will not take into account the changes to the software. I'll be sticking to DAZ Originals for some months to come from now on. If you meant "World Garden Maze" product it's not a DAZ Originals so doubt it'll be updated.
If your having problems with Aiko 6 I'd definately put a ticket in and report it, the more problems that are officially reported the more likely they are to fix the problems.
Others have also reported similar problems since the upgrade, so it maybe something that will be changed with future bug fix.
From a technical point of view I think Carrra uses OpenGL to pre-view a scene so it will be dependant on your graphics cards memory size as to how large a scene you can preview.
Have you tried clearing out your temp directories and done disc drive housekeeping (Right click on C: drive/select properties/ select tools tab/click optimise) may possibly be running short of space on your drive (have you checked free space size?)
Hope this helps.
Videatoculo(Jedi Tea Master - Come over to the darkside, we have Assam and biscuits!)