But: When there is a timed recording, vdr tries to get data by restarting, which is naturally the wrong way to try to receive an EMM from the cable...
Naturally, when there is a valid EMM already on the card, there are no problems in either case, but decrypting starts immediately.
VDR doesn't "try to get data by restarting". When a recording is active, and there is no data received for a certain time, VDR assumes that there is something wrong with the driver/firmware/whatever and initiates a reload of the driver (actually the surrounding wrapper script is supposed to do this, so VDR just exists with a specific return value).
In my setup with FF-DVBC + Conax CAM + legal card and budget DVBC-card this made my system to continuously restart. Only thing to stop this was logging in into VDR-machine, editing timers.conf and disabling the timer.
Restarting was done so quickly that I could press just one remote control key, but could not disable timer via OSD.
And reloading driver didn't help for the problem. Problem was that ECM didn't happen to card on certain channels.
So perhaps CAM error should be analyzed before making a decision what to do? No valid key on card = just warn user, CAM not responding = reset CAM, no DVB data = reload driver?