The lines are indicating the LQI. Check the LQI values to see whats going on.
LQI’s are reported by the devices. If the devices report it incorrectly, it might give wrong results. As with your other post : ZBmini these seem to have firmware inconsistencies already. I wouldn’t be amazed if their LQI calculation is not up to par either.
It’s basically a quality thing on the devices and really hit or miss. Personally, i never check the LQI’s or colors: if they work they work, if they don’t I’ll investigate. I really couldn’t care less for their link quality as it’s often reported wrongly.