partial warning, prints OK?!

[Albert Einstein]

I have music for five instruments - ChoirStaff in v. 2.2.5.
For second and third staff I get warnings: barcheck failed at: -1/4:; 
prints is OK, and manual calculating pass.

When I lilypond separetly the staffs I don't get this warnings.

Albert

$ lilypond mt.ly
lilypond (GNU LilyPond) 2.2.5
Running lilypond-bin...
Now processing `mt.ly'
Parsing...
Interpreting music... [8][16][24][32][40]
/home/Admin/mt.ly:244:8: warning: barcheck failed at: -1/4:
\partia
       l 4

/home/Admin/mt.ly:391:8: warning: barcheck failed at: -1/4:
\partia
       l 4  r4 %\bar ":|:"
[48][56][64][72][80][88][96][104][112][120][128][136][138]
Preprocessing graphical objects...
Calculating line breaks... 
[3][6][9][12][15][18][21][24][27][30][33][36][39][42]
[45][48][51][54][57][60][63][66][69][72][75][78][81][84][87][90][93][96][99][102
][105][108][111][114][117][120][123][126][129][132][135]

paper output to `mt.tex'...
writing header field `fontencoding' to `mt.fontencoding'...
writing header field `composer' to `mt.composer'...
writing header field `arranger' to `mt.arranger'...
writing header field `title' to `mt.title'...
writing header field `inputencoding' to `mt.inputencoding'...


Analyzing mt.tex...
Running ...
Running dvips...
Running ps2pdf...
DVI output to `mt.dvi'...
PDF output to `mt.pdf'...
PS output to `mt.ps'...