Charles,
I have used Titegroup in loads like you have stated. One characteristic of it is that it is supposed to be position insensitive. I have never noticed it being position sensitive even in light loads like you are loading. What does the data say is the minimum load for your bullet type? Are you below it? If so, that is a no-no and may be the reason for your problem.

Check the data.

p.s. Personally, I don't like Titegroup for one of the reasons you mentioned, case fill. With the recommended loads there is still a lot of room in the case. Easily enough to even put a triple charge in there let alone a double!