I just released a new major beta version (0.3) of Auctioning that doesn't have any big new features as most new major versions (0.x versions) do but there were so many bug fixes and small changes that it was fitting. One of the big new things is that when you do a post or cancel scan, before the scanning starts, Auctioning will check to make sure all your groups are valid. Mainly, if you are using a % of something as a threshold / fallback, that all the items in the group evaluate to the exact same amount (ie if you are using % of crafting cost, all the items have the same mats or if you are using % of auctiondb market value, there is only one item per group). If it finds invalid groups, it'll offer to fix them for you automatically. What it will do is just convert the group into a category...and create enough groups inside that category so that they are all valid.
For a full list of changes see the changelog.