Time bar

[Forest]

Hello, new user here. Please can anyone explain why the blue time bar, on the playback function, showes vertical black lines. When playing back, a black line is skipped, the time jumps as well. I would have thought the blue time bar would be solid unless punctuated by an event such as vehicle or person detected. I understand red lines are events but black ones, I don't know.
Thanks for any help.

 

[Marco Hill]

If I am not mistaken the black lines show there is no recording for that time. Do you have your NVR/Camera's on full time recording?

Do you have network/power problems that might stop the system from operating thus not record.