COPX alt not shown in Tag

Ok, so the catching seems not to be the issue. Possibly the performance? If a COP level cannot be reaching according to the ES performance (climb/descend) calculations, it will not show it anymore in the label. You can test it by either increasing the distance of the aircraft to the point, or lower its altitude.
I think this was also recently discussed because of the limited update options. So possibly, the aircraft type may have an influence as well.