Subplot in movie

Hi there,

I have some trouble using subplot within the movie module …

# # # # # # # # # # # # # # # # # # # # # # # # # # # #
#                                Main.sh                                  #
# # # # # # # # # # # # # # # # # # # # # # # # # # # # 
gmt begin
gmt grdfilter \${region} \${data}"?u[\${MOVIE_COL0}]" -Fm5 -D4 -I5 -Gtmp_u.nc
gmt grdfilter \${region} \${data}"?v[\${MOVIE_COL0}]" -Fm5 -D4 -I5 -Gtmp_v.nc

gmt subplot begin 2x2 -M2c -Fs15c \${region} \${projection} -T"\${titre}" -Bwesnlbtr

# TL
gmt grdimage -Ca.cpt \${data}"?a[\${MOVIE_COL0}]" -c0,0

# TR
gmt grdimage -Cb.cpt \${data}"?b[\${MOVIE_COL0}]" -c0,1

# BL
gmt grdimage -Cc.cpt \${data}"?c[\${MOVIE_COL0}]" -c1,0

# BR
gmt grdimage -Cd.cpt \${data}"?d[\${MOVIE_COL0}]" -c1,1
gmt grdvector tmp_u.nc tmp_v.nc -W\${v_pen}c,black -Gblack -Si\${v_scale}k -Q\${v_head}c+e+a45+jc+n\$(echo "scale=3; \${v_scale} * 25;"|bc)k

gmt subplot end
gmt end
EOF

# # # # # # # # # # # # # # # # # # # # # # # # # # # #
#                                 Post.sh                                  #
# # # # # # # # # # # # # # # # # # # # # # # # # # # # 

cat << EOF > post.sh
gmt begin 
gmt subplot begin 2x2 -M2c -Fs15c \${region} \${projection} -A  -Bwesnlbtr

# TL
gmt coast -Dc -Wthin -c0,0
gmt colorbar -Ca.cpt \${clr_sty} \${clr_atxt}

# TR
gmt coast -Dc -Wthin -c0,1
gmt colorbar -Cb.cpt \${clr_sty} \${clr_btxt}

# BR
gmt coast -Dc -Wthin -c1,0
gmt colorbar -Cc.cpt \${clr_sty} \${clr_ctxt}

# BL
gmt coast -Dc -Wthin -c1,1
gmt colorbar -Cd.cpt \${clr_sty} \${clr_dtxt}
gmt legend -DjTR+w2c+o-5p/1p -F+r4p+pthinnest,gray+gwhite --FONT_ANNOT_PRIMARY=8p <<- END
S - - \$(echo "scale=3; 25 * \${v_scale}/111.132954 * \${map_cm}/(\${lonE}-\${lonW});"|bc)c black \${v_pen}c - 25m.s@+-1@+
END

gmt subplot end
gmt end
EOF

This already plot two frames (one is simple, the other is fancy) on top of each other, and they are not perfectly aligned …

If I want to add a title to each subplot by adding -B+t"a title" in post.sh, this shift is even more apparent.

If I use some annotation say, -Bx30f10 -By10f10 instead of -Bwesnltrb in post.sh, of course they overlap.

Am I missing something ?