gstreamer – Why is FFmpeg creating an inconsistent number of fragments in MPEG-DASH?

Context:
I’m using GStreamer to receive an RTP MPEG-TS stream from a multicast camera, process it, and forward it via UDP to FFmpeg, which then generates low-latency MPEG-DASH segments.

Problem:
I expect exactly 20 fragments per 4-second segment (frag_duration=0.2, seg_duration=4), but FFmpeg sometimes creates 15, 18, or 23 fragments instead.

Gstreamer Pipeline

udpsrc address=
 port= do-timestamp=true timeout=60000000000 buffer-size=1310172 caps="application/x-rtp,media=(string)video,clock-rate=(int)90000,encoding-name=(string)MP2T,payload=103" ! rtpbin name=recv_rtp ! rtpjitterbuffer ! queue ! watchdog timeout=10000 ! rtpmp2tdepay tts=true ! queue ! tsparse set-timestamps=true ! tsdemux wait-pcr=false ! h264parse ! video/x-h264,stream-format=byte-stream,alignment=nal ! rndbuffersize max=65000 ! queue ! udpsink host=127.0.0.1 port=6311 max-lateness=0

here is my ffmpeg command

ffmpeg  -loglevel debug -probesize 32  -analyzeduration 0 -i udp://127.0.0.1:6311?buffer-size=1310172 -fflags +nobuffer -flags low_delay -err_detect ignore_err -c:v copy -c:a copy  -g 10 -keyint_min 10 -sc_threshold 0 -movflags +frag_keyframe+empty_moov+default_base_moof -window_size 30 -extra_window_size 15 -use_template 1 -use_timeline 0 -streaming 1 -adaptation_sets "id=0,streams=v id=1,streams=a" -utc_timing_url "http://time.akamai.com/?iso" -write_prft 1 -index_correction 1 -seg_duration 4 -frag_duration 0.2 -frag_type duration -flags +global_header -format_options "movflags=cmaf" -ldash 1 -target_latency 2.0  -http_persistent 1 -f dash manifest.mpd

Running MP4Box -info .m4s shows an inconsistent number of fragments per segment.
The number of fragments varies, though frag_duration is fixed at 0.2s.

I want exactly equal number of fragments to ensure smooth playback. Any insights into the cause of this variation and possible solutions would be greatly appreciated.

Thanks in advance!