Unitiserve flac reproduction problem

Hi to everyone,

I own a fresh unitiserve 2tb and I have a few problems with flac reproduction.

The connection I use is unitiserve to audiolab m-dac with naim digital cable and from m-dac to naim nac282 with other digital cable.

The flac files are saved at the internal hdd, in the downloads folder, at their own folders per album.

So, my problem is that, when listening to them, there are times that the audio is not gapless, but stops for a second and continues.

This is not often.

If I stop the music and restart it, I might not have the audio gap of that second.

There are times that I listen to the same files and the audio is gapless.

Are there any settings to change that might correct the problem ?

The problem is not constant, why is very strange...