thank you,
have clone the eMMC to sdcard, and repurposed the eMMC for the LibreElec - it seem the problem is no longer occuring.
however, one another SBC have similar issue,
one eMMC is android, and CoreElec on SDCard, then however, when both are loaded, the videoplayback is garbled on times on CoreElec 22.
it seem for one reason or another not liking to have both eMMC and sdcard present at the same time when booting;
on CoreElec there would be an option to "reboot to eMMC" which would be handy on TV , to boot into fully Android or Linux on demand from within CoreElec , but then if the LibreElec/CoreElec is having issue if eMMC is present it is not worth it.
(this SBC however uses a Pine A64 eMMC and the sbc itself is from Odroid, which seem to sell there own branded eMMC)