On 05/05/2021 23:09, Bob Eager wrote:
Over the years, I have operated the same reliable HP 4M+ printer.

I have had this exact effect on a number of occasions. In every case it
was caused by a faulty toner cartridge (but remember that quite a lot of
the 'works', e.g. optical drum, corona wire) are inside their cartridges.
In most cases, I think they were 'old stock' cartridges. Reputable
remanufactured ones work fine.

Thats the conclusion I am coming to as I have dismantled and cleaned the
cart twice. I suspect the issue is the the compartment that collects
excess toner possibly leaking on to a roller. The cart is a remanufactured.