Shortly after posting the messages stopped, and haven't appeared for about 30 minutes now.
I'm guessing the software must have created a "queue" of incomplete print commands (though nothing showed in the print queue) which have now been exhausted.
OnePlus 5 review
Alice Saey's mesmerising animation for Dutch singer Mark Lotterman
iPad Pro 10.5in (2017) review
Comment booster votre iPhone ?