Two times I am trying to write text within a textbox into a graph. However, although the commands for both text boxes are identical (except for the text), only the first text is centered correctly, while the second is not (if I exchange the sequence of the commands for the text boxes, again the first is correctly centered while the second is not).

I am not sure whether there is an error on my part or whether this is a problem with Stata. Here is the (somewhat lengthy) code I am using (see my comments marked in red):
Code:
* set scheme lean1 (install scheme if necessary):
cap set scheme lean1
if _rc {
  net install gr0002_3, from("http://www.stata-journal.com/software/sj4-3")
  set scheme lean1
}

local m0 = 68
local m1 = 69
local sd = 3.1
local  n = 100
local se = `sd'/sqrt(`n')
local alpha = 0.05
local z = invnorm(1-`alpha'/2)
local lower = `m0'-`z'*`se'
local upper = `m0'+`z'*`se'
if `m0' < `m1' {
  local beta = normal((`upper'-`m1')/`se') - ///
               normal(-(`m1'-`lower')/`se')
  local crit = `upper'
  local area1 = max(`lower',`m1'-4*`se')
  local area2 = `crit'
}
else {
  local beta = normal((`m1'-`lower')/`se') - ///
               normal(-(`upper'-`m1')/`se')
  local crit = `lower'
  local area1 = `crit'
  local area2 = min(`m1'+4*`se',`upper')
}
local power = 1-`beta'

local tcrit : di round(`crit',0.01)
local tbeta : di round(`beta',.001)
local tpower : di round(`power',.001)

local xtit1 = "kritischer Wert = `tcrit', {&alpha}{subscript:zweiseitig} = `alpha', "
local xtit2 = "{&beta} = `tbeta', Power = `tpower'"
local subt1 = "{it:n} = `n', H{subscript:0}: {&mu} = `m0', "
local subt2 = "H{subscript:1}: {&mu} = `m1', {&sigma} = `sd'"

twoway function y=normalden(x,`m0',`se'), ///
                range(`=`m0'-4*`se'' `=`m0'+4*`se'') ///
                recast(area) color("255 255 212") || ///
       function y=normalden(x,`m1',`se'), ///
                range(`=`m1'-4*`se'' `=`m1'+4*`se'') ///
                recast(area) color("255 255 212") || ///
       function y=normalden(x,`m0',`se'), ///
                range(`=`m0'-4*`se'' `=`m0'-`z'*`se'') ///
                recast(area) color(blue) || ///
       function y=normalden(x,`m0',`se'), ///
                range(`=`m0'+`z'*`se'' `=`m0'+4*`se'') ///
                recast(area) color(blue) || ///
       function y=normalden(x,`m1',`se'), range(`=`area1'' `=`area2'') ///
                recast(area) color("240 59 32") || ///
       function y=normalden(x,`m0',`se'), ///
                range(`=`m0'-4*`se'' `=`m0'+4*`se'') color(black) ///
                lw(vthin) lp(solid) || ///
       function y=normalden(x,`m1',`se'), ///
                range(`=`m1'-4*`se'' `=`m1'+4*`se'') color(black) ///
                lw(vthin) lp(solid) ///
       title("Power eines Einstichproben-{it:z}-Tests", size(medsmall)) ///
       subtitle("`subt1'`subt2'", size(small)) ///
       xtitle(`"`xtit1'`xtit2'"', size(small)) xlabel(`m0' `m1', labs(small)) ///
       text(0 `m0' "{&mu}0", size(vsmall) place(s)) ///
       text(0 `m1' "{&mu}1", size(vsmall) place(s)) ///
       text(0 `=`crit'' `"`tcrit'"', size(vsmall) place(s) col(blue)) ///
       ytitle("Wahrscheinlichkeitsdichte", size(small)) ylab(, labs(small)) ///
       text(0.6 68 "Akzeptanz-" "region H{subscript:0}", size(6pt) place(c) /// // <-- correctly centered
            box bc(white) fc(white) lstyle(none) bex) ///
       text(0.6 69 "Akzeptanz-" "region H{subscript:1}", size(6pt) place(c) /// // <-- not centered
            box bc(white) fc(white) lstyle(none) bex) ///
       legend(off) scheme(lean1)