S928X (Ugoos AM8 Pro): CMA memory leak during hardware video playback leading to Kodi crash and watchdog reboot Environment

    Device: Ugoos AM8 Pro
    SoC: Amlogic S928X
    RAM: 8 GB
    Boot medium: microSD
    CoreELEC versions tested:
    22 Alpha 1
    22 Alpha 2
    22 Alpha 3
    22 Beta 1
    DTB: stock am8 DTB supplied with each respective release
    Kodi: bundled with CoreELEC
    Playback:
    Native Jellyfin integration
    Media stored on NFS mount (kernel-level mount)
    Display:
    1080p projector
    SDR only
    No HDR
    No Dolby Vision

    Problem
    During hardware video playback, contiguous CMA memory gradually decreases until Kodi crashes and the system reboots.
    Typical failure sequence:
    Video plays normally.
    Audio begins looping the last buffer.
    Screen turns black.
    Kodi crashes.
    Device reboots (watchdog).
    The problem only occurs during video playback.
    System is stable indefinitely when:
    idle (tested for 5 days)
    playing music
    browsing the UI

    CMA observations
    Initial:
    CmaFree ≈ 1985 MB
    During failing playback:
    44 min: CmaFree ≈ 1141 MB
    51 min: CmaFree ≈ 792 MB
    58 min: CmaFree ≈ 410 MB
    (examble on Sherlock Holmes 2009)

    After stopping playback:
    CmaFree recovers only partially (approximately 670 MB), never returning to the initial value.
    Starting another video after this can causes an immediate crash if little of memory was left.
    Normal system RAM does not show a comparable increase.

    Debugging performed
    Fresh SD card formatted before every installation
    No restored userdata
    Multiple CoreELEC versions tested
    Different Arctic and stock estuary skins tested
    Debug logging enabled
    CMA monitored through:
    grep -i Cma /proc/meminfo 
    DMA-BUF inspection:
    cat /sys/kernel/debug/dma_buf/bufinfo 
    Result remains constant:
    3 DMA-BUF objects
    ~87 MB total
    No increasing exported DMA-BUF count was observed.
    Kernel log before reboot contains only repeated:
    dim:warn:irq:flag 0 
    No GPU fault, kernel panic, or OOM messages appear before SSH connection is lost.

    Codec testing
    Initially AV1 appeared stable, but further testing showed codec alone is not the determining factor.

    Failing file
    Alice in Wonderland
    MKV
    AV1 Main
    1920×1080
    10-bit
    23.976 fps
    AV1 codec string: av01.0.08M.10.0.111.01.01.01.0
    Video bitrate: ~8.18 Mb/s
    DTS-HD MA + DTS + AC3
    2 PGS subtitle tracks
    Result:
    Rapid CMA depletion
    Crash after approximately 20 minutes

    Working file
    Project Hail Mary
    MKV
    AV1 Main
    1920×1080
    10-bit
    24 fps
    AV1 codec string: av01.0.08M.10.0.110.01.01.01.0
    Video bitrate: ~0.77 Mb/s
    HE-AAC stereo
    35 SRT subtitle tracks
    Result:
    Over 2 hours playback
    No measurable CMA leak

    Additional testing
    Disabling subtitles does not resolve the issue.
    Hard factory reset, stock skin, file played from usb flash drive, movie stripped from everything except video track - no subtitles, audio, tags, chapters etc - leak stills occurred but slower
    FFmpeg software decoding reports no bitstream corruption.
    Audio playback alone never reproduces the problem.
    System idle for multiple days remains stable.

    Additional information
    Im not an IT person report above is an export from AI chat after 3 days of trouble shooting and hitting the wall time and time again - if any additional information is necessary, please word it in a way layman can understand.
    Approximately 80% (if not more) of my movie library of hundreds of movies are causing problems both files ripped from BD and transcoded by me as well as privatized from internet h264, h265, av1 all cause problems - tho movies and tv series with low bit-rate are in general less problematic than high quality rips

    older logs as i just wiped installation to try again with clean sheet and all logs perished but the SIGSEGV is consistent with current crashes - the Crash in FT_Done_Face / FreeType was resolved by overwriting subtitles styles