Problem Zsight on IOS


I am using the latest version of Zsight on IOS, version 1.3.88

It works great but i notice one problem:

When i choose playback (when i am on location of the nvr) and choose
a channel and date i can see the recorded video.
But, in the time-bar i see some very small white lines.
When the video comes to such a line, it says “No recorded video”.

I dont understand the white lines, because in my nvr i have continously recording without any alarm/motion".
When i look on an android phone all works fine (no white lines).

Can anyone explain this?