Blog page load issue and web page load icon issue

Couple of issues that I just can’t find a solution for. Wondered if anyone had any ideas!
So I created my website https://www.babyworldandme.co.uk/ and have just created a sub domain staged environment for testing and then duplicated my site onto that. On the testing site I’ve just created a child theme and got everything up and running.

1st issue: Whilst my test site runs perfectly there are a couple of issues on my main site. First of all the blog page. When I click on this with a clear cache instead of displaying as a masonry grid straight away it left aligns vertically and overlaps so looks awful. Click again and it goes back to a masonry grid like it should – although intermittently will then recreate the issue again. My test site works perfect every time even though it’s duplicate settings? Any ideas? I’ve tried in different browsers and devices and get the same problem.

2nd issue: My test site (sub domain) shows a responsive loading icon in the centre at peak times then loads the page smoothly but my main site never shows this and seems to load in – how shall I put it – quite a jerky fashion. Again, I have no idea why! I’ve tried in different browsers and devices and get the same problem.

Thanks in advance and just a heads up I’m a one month wordpress novice learning as a I go!