I have my fingers crossed that someone will resolve this soon. I've been trying for ages to unsubscribe from this.
Thank you Ṣmeed for your suggestions that I move my thread to CPC and to also report the problem in the Performance Issues thread.
To all those affected by this problem, I wish you well.
PS I'm NOT clicking the "Notify me" box below***. In theory, I shouldn't receive any more notification emails, should I!
*** when I drafted this.