problems with using ffmpeg on RPi4 and LE10.0.4 (Matrix)

I am using IPTV Recorder addon either on LE9.2.8 or LE10.0.4 on RPi4B as well as RPi400. Both SW platforms use ffmpeg application (ported by LibreELEC team) with exactly the same parameters (!!! - I compared the code of calling ffmpeg on both SW platformas) to record an IPTV stream on SD card of RPi. The same stream recorded on LE9.2.8 is perfect in quality when played back, whereas that recorded on LE10.0.4 is blurred, hanging times to times. I am 100% sure it is not related to the quality of input stream as I recorded the same stream at the same moment on both SW platforms. Versions of ffmpeg executable are different on both SW platforms. Is (may) it be related to problems with ffmpeg application on Matrix? On LE10.0.4 I tried different versions of ffmpeg available. I was not able to test the case on LE11.0.1 as IPTV recorder is not working on NEXUS although Publisher3r review its IPTV Recorder addon to Nexus version about 2 month ago. I can install his addon on NEXUS on RPi4 howewer it cannot integrate with IPTV Simple.