Audiomeca Enkianthus DAC problem

Dear Audiogoners – about a month ago my DAC started to go show some strange symptoms: After correctly “locking” to my transport, it plays first CD without interruptions. When second (sometimes third) CD is inserted, there is no signal leaving DAC (while “lock” between DAC and transport remains on). This behavior also occurs while the transport is in the “shuffle” mode – in this case the signal from DAC disappears after 3-4 songs tracks being played.
What could be the reason for this behavior? Thank you in advance for your thoughts…
Lucian