In order to do a trace and if you do neither have morly's tool nor serial connection you could log into via telnet, then use
killall rcS; killall enigma2
(ensure that no-one is using the box at this stage or no recordings are ongoing, otherwise you risk a divorce )

After that start the software again with
enigma2
After that you get all output to the telnet window (better do a capture of the output as it is quite a lot coming there) and you could repeat your tests and provide the output here. Please remember to reboot the box after tests are done to get it into normal shape.

And about the visible issue: I did not mean that it only happens with recordings but also it could happen there. It can also happen when using standard player to play recorded movies and as you mentioned when either playing music or videos via media center.