Update:
After contact with the seller I got sent a new toner.
Contact was very nice and accommodating.
The new toner I have now received and will now watching how long it holds now.
Should he now the promised performance hold then I'll change the review nor 5 star.
Update:
the replacement toner I've got now runs flawlessly.
has already ca 1000 pages printed and still shows no signs of slowing.
After the initial difficulties have ink service by the great service now 5 star worthy.