Graphs appear with delay on refresh

[silke-99]

Please don't delete these questions! They are asked almost with every issue - answering them as below saves us time from asking them!

First step
I tried debugging but didn't see any errors (apart from a highcharts warning for accessibility.js which I addressed).

Describe the bug
When accessing or refreshing any page with graphs e.g. Belchertown start page or dedicated grapg pages, it takes longer than normal for the graphs to appear. On my website start page, it takes around 20 secs to load graphs after the rest of the page has finished loading.

I believe this did not happen in the past (I'm a long time happy Belchertown skin user) and it probably appeared only in recent days/weeks. Unfortunately I can't pinpoint exactly when the issue started.

Link to your website (IMPORTANT)
https://cosmospace.cc/

Version of the skin you're using
1.3.1

To Reproduce
Go to my website and start counting :-)

Expected behavior
graphs should appear along with the rest of the page.

Screenshots
n/a

Device Information (please complete the following information):
Chrome, Firefox, multiple devices

Additional context
No idea. I did upgrade to weewx5 a few days ago, but I think the issue started before that.

Any idea? Thank you all!