I'm glad that you contacted support. I have myself, and I know others who have brought up similar issues here in the forum claim they have as well.
One thing you didn't respond to is exactly which of the three "Relationship Calculators" you're on about. Have you tried using the Relationship Calculator under the tools menu? If it detects the relationship you want, then you can create a chart from there--you just can't edit any of the chart's options.
The discussion of compromised data is at this point academic. The shortcomings of the parts of FTM that calculate relationships, thankfully, do not alter the data in your tree, but they do make it difficult to find and report multiple relationships. Most of us purchase genealogy programs because they're supposed to make that sort of thing easier.
As the kids today say, EPIC FAIL.