This is really strange your running the same setup as me.
Must not have exactly the same packages installed.
Try replacing the local_trailing_rate_graph() with this code. This is a version of local_rate_graph_24ma() posted previously in this thread. The only problem with this code is when using older versions of rrdtool when there is no data available to calculate averages the yellow area disappears for that portion of time.
local_trailing_rate_graph() {
rrdtool graph \
"$1" \
--start end-$4 \
--width 1110 \
--height 200 \
--step "$5" \
--title "$3 Message Rate (Trailing)" \
--vertical-label "messages/second" \
--lower-limit 0 \
--units-exponent 0 \
--right-axis 360:0 \
--slope-mode \
"DEF:messages=$2/dump1090_messages-local_accepted.rrd:value:AVERAGE" \
"DEF:a=$2/dump1090_messages-local_accepted.rrd:value:AVERAGE:end=now-86400:start=end-86400" \
"DEF:b=$2/dump1090_messages-local_accepted.rrd:value:AVERAGE:end=now-172800:start=end-86400" \
"DEF:c=$2/dump1090_messages-local_accepted.rrd:value:AVERAGE:end=now-259200:start=end-86400" \
"DEF:d=$2/dump1090_messages-local_accepted.rrd:value:AVERAGE:end=now-345600:start=end-86400" \
"DEF:e=$2/dump1090_messages-local_accepted.rrd:value:AVERAGE:end=now-432000:start=end-86400" \
"DEF:f=$2/dump1090_messages-local_accepted.rrd:value:AVERAGE:end=now-518400:start=end-86400" \
"DEF:g=$2/dump1090_messages-local_accepted.rrd:value:AVERAGE:end=now-604800:start=end-86400" \
"DEF:amin=$2/dump1090_messages-local_accepted.rrd:value:MIN:end=now-86400:start=end-86400" \
"DEF:bmin=$2/dump1090_messages-local_accepted.rrd:value:MIN:end=now-172800:start=end-86400" \
"DEF:cmin=$2/dump1090_messages-local_accepted.rrd:value:MIN:end=now-259200:start=end-86400" \
"DEF:dmin=$2/dump1090_messages-local_accepted.rrd:value:MIN:end=now-345600:start=end-86400" \
"DEF:emin=$2/dump1090_messages-local_accepted.rrd:value:MIN:end=now-432000:start=end-86400" \
"DEF:fmin=$2/dump1090_messages-local_accepted.rrd:value:MIN:end=now-518400:start=end-86400" \
"DEF:gmin=$2/dump1090_messages-local_accepted.rrd:value:MIN:end=now-604800:start=end-86400" \
"DEF:amax=$2/dump1090_messages-local_accepted.rrd:value:MAX:end=now-86400:start=end-86400" \
"DEF:bmax=$2/dump1090_messages-local_accepted.rrd:value:MAX:end=now-172800:start=end-86400" \
"DEF:cmax=$2/dump1090_messages-local_accepted.rrd:value:MAX:end=now-259200:start=end-86400" \
"DEF:dmax=$2/dump1090_messages-local_accepted.rrd:value:MAX:end=now-345600:start=end-86400" \
"DEF:emax=$2/dump1090_messages-local_accepted.rrd:value:MAX:end=now-432000:start=end-86400" \
"DEF:fmax=$2/dump1090_messages-local_accepted.rrd:value:MAX:end=now-518400:start=end-86400" \
"DEF:gmax=$2/dump1090_messages-local_accepted.rrd:value:MAX:end=now-604800:start=end-86400" \
"DEF:strong=$2/dump1090_messages-strong_signals.rrd:value:AVERAGE" \
"DEF:positions=$2/dump1090_messages-positions.rrd:value:AVERAGE" \
"CDEF:y2strong=strong,10,*" \
"CDEF:y2positions=positions,10,*" \
"SHIFT:a:86400" \
"SHIFT:b:172800" \
"SHIFT:c:259200" \
"SHIFT:d:345600" \
"SHIFT:e:432000" \
"SHIFT:f:518400" \
"SHIFT:g:604800" \
"SHIFT:amin:86400" \
"SHIFT:bmin:172800" \
"SHIFT:cmin:259200" \
"SHIFT:dmin:345600" \
"SHIFT:emin:432000" \
"SHIFT:fmin:518400" \
"SHIFT:amax:86400" \
"SHIFT:bmax:172800" \
"SHIFT:cmax:259200" \
"SHIFT:dmax:345600" \
"SHIFT:emax:432000" \
"SHIFT:fmax:518400" \
"SHIFT:gmax:604800" \
"CDEF:7dayaverage=a,b,c,d,e,f,g,+,+,+,+,+,+,7,/" \
"CDEF:min1=amin,bmin,MIN" \
"CDEF:min2=cmin,dmin,MIN" \
"CDEF:min3=emin,fmin,MIN" \
"CDEF:min4=min1,min2,MIN" \
"CDEF:min5=min3,gmin,MIN" \
"CDEF:min=min4,min5,MIN" \
"CDEF:max1=amax,bmax,MAX" \
"CDEF:max2=cmax,dmax,MAX" \
"CDEF:max3=emax,fmax,MAX" \
"CDEF:max4=max1,max2,MAX" \
"CDEF:max5=max3,gmax,MAX" \
"CDEF:max=max4,max5,MAX" \
"CDEF:maxarea=max,min,-" \
"LINE1:min#FFFF99:mins" \
"AREA:maxarea#FFFF99:max:STACK" \
"LINE1:7dayaverage#00FF00:7 day average" \
"AREA:y2strong#FF0000:messages >-3dBFS / hr (RHS)" \
"LINE1:y2positions#00c0FF:positions / hr (RHS)" \
"LINE1:messages#0000FF:messages received" \
--watermark "Drawn: $nowlit";
}