I have the same opinion as johnnydialtone.

If you didn't spin check your bh's , YOU NEED TO.
Even the best tuned bow can't group bh's if your heads are crooked.
Get a bh spinner and tune your arrows. The fact that you had erratic flight at different distances and there was no apparent pattern would tell me the heads are not straight on the shaft.
Once you make sure of that , then you can go to the bow tuning process.
I'm sure that both are needed.