OK, just to update. The problem returned in most browsers I tested, so, I again switched OFF WP Fastest Cache [WPFC] and am leaving it off for now. The site now loads and loads faster on all major browsers tested.
WPFC has served me well on multiple sites, but for some reason, seemingly not this one.
Is there a fundamental problem, in NOT using a cache on a site?
I’ve seen online advice, suggesting sites which use CloudFare [mine DOES] do not necessarily need caching? If it’s best however to use a cache, suggestions for an easy to set-up alternative to WPFC please? Thank you.