For 1099-R, why would Turbotax shift a small portion of total from line 5B to 4b

i have 4 1009-R, 2 for  pension/annuity, 2 normal distributions.  all '7'.   a small portion of the pension/annuity being reported in 4B, not 5B.  Is Turbotax at fault?  total between 4B and 5B ok,  and the drill down shows me the proper 1099-R