My apologies for not replying sooner! Lately, I have not been able to reproduce the 'straightening' tool problem. My Affinity Photo is 1.7.0 and my Mac Operating System is 10.14.5. Thank you for the links for reporting a bug. My original description of the bug is, as was described in my original post. Perhaps the computer just needed a restart?
In future I will, should I encounter a 'bug', use the protocol in the link.
I was personally disappointed to see a link to 'Unsplash', the Stock website. While it's choice, if photographers don't put a value on their work, no one else will. Unsplash undermines those photographers who are attempting to earn a living from their work. I don't think Affinity should encourage such a thing. Are your programs free?