clicks with spdif audio recording

Let's go with my problem:

While recording from my spdif input to audio track in logic i can hear clicks. These clicks are more frequent as lower is the core audio buffer. I can deduce where around is the problem, but how to solve it? (I'm sure my usual buffer size settings are enough, 64 samples buffer works great with many exs instruments, large cpu load and without clicks)

I hope I'm missing something and this is not a bug. I've set the audio card clock as external. Sample rate detected 48khz. That's ok. I can monitor the input signal through the analog output. It sounds fine and polite. (So my device is working correctly)

I don't know what exactly i have to do with audio configuration in logic to record properly in this scenario. I've set the audio sample rate obviously to 48khz, i've tried several synchronization settings as external, autodetect external sync, etc. All of them (even with the standard settings) produce the same bahaviour. Tried turning off software monitoring. The same.

Can anybody help me or give some advice?
Thanks