Problem with specific color streaking from a possible damaged printhead

[The Hat]

As I stated, the test patterns test good.

In all likelihood, a new original Canon cartridge would solve the problem.

this is best option..

 

[videobruce]

Considering that you say the nozzle check is good, that photo shows the typical effects of bad inkflow ( also called ink starving), on the magenta channel. It can be a cartridge problem (sponge clogged with dried ink) or the ink itself being in bad shape. As you say its 'a bit' old.
In all likelihood, a new original Canon cartridge would solve the problem.

It appears that it was a songe problem as I swapped a newly filled virgin cart and it looks like it prints fine (so far).