ACV

what the crap does that mean?

Okay, so you have a solid RAR file that ACV cannot view.

I do not think you should assume from your test that it is always impossible to view solid RAR files. The difference between a solid and not solid archive file is more compression* and that means more work to unpack a file. It could just be that the particular file you tested was too big and too much work although ACV tried to work (even with poor performance) and that extra bit of work was just too much and ACV did the best it could but your phone failed. If that is the case then this is just another example of the known problems with RAR files.
RAR support seems like a problem that will eventually solve itself as people get more powerful phones but in the meantime the small saving of storage space RAR gives causes far more problems than it is worth, but RAR makes such a small improvement over ZIP I don't know why anyone uses it.

[* Further explanation of solid archive: A solid archive packs the whole set of files as one big group and compresses them all. This crushes things smaller but it does mean that to unpack the whole entire set must be unpacked before even one file can be viewed.
In contrast ZIP compresses each file individually, and a ZIP archive can even contain some heavily compressed and other files such as a list manifest with little or no compression to allow fast access of just one file. This can be very useful for file formats like OpenDocument, and OpenXML, and CBZ.]