When waking from sleep. backlight is intermittent as display is raised. Examination shows that the image is always there, but the lighting is dependent on display/top cover position. But, the inverter cable may not be the problem. Could be loose/dirty plug, etc.
Haven't replaced cable yet, as the computer is useable. Will do when I have time. Will check existing cable and if it's OK will send the replacement back to IFixit, along with another G4 laptop for parts.
Don't know if this is a common problem; will see how it does after inverter cable replacement.