I know it goes against common theory, as you're getting a weak arrow indication, but sometimes it's really an indication of the arrow being too stiff. You could try making adjustments opposite of what you'd think.
I always bare shaft tune my setups and get a tail-left bare shaft, which would indicate a weak arrow, but most times it's just the opposite. I can usually confirm this by shooting a stiffer spine and the reaction gets worse---farther right and angled harder.
Two things. One, I rarely shoot a bow maxed out. Two, if my bare shaft planes to ne side or the other I rarely ever move my rest. I adjust the draw weight up or down. This allows me to see just which way I need to go. From experience I usually know anyway whether to add or subtract weight.
As an example, I have a Martin Moab that I'm shooting at 47# and 26.5" draw. Theoretically I should be shooting about a 600 spine. I tried a 560 (ACC 3-18, 27" shaft) and it wasn't good. Arrow planed to the right, tail-left. Weak arrow? I then shot a 500 (ACC 3-28) and then a GT 22 Series (300 spine), In each case the planing got worse, with the arrow planing farther right and tail left at about 45 degrees. All this shows me is that I was not getting a weak arrow reaction, but one that is too stiff. Without moving the rest, but adding draw weight I was able to get things straightened out better.
I have an older version of Easton's Tuning Guide and reading the next to last paragraph on page 13 describes this fairly well. In assense it says that releae shooter sometimes get an opposite indication then that of finger shooters when bare shaft tuning. Make your adjustments accordingly.