Hi,
According to your description, my understanding is that when you reference Jquery accordion control in master page, it is not working and the page which reference the Jquery loads slowly.
For a better troubleshooting, I suggest you can use Internet Explorer Developer Tool (F12) to check if the Jquery file has been load correctly and if there are some error message in the page. You can see the Jquery loading time using Internet
Explorer Tool like the capture below, then you can see which file leads to load page slowly.

More information:
How to use F12 Developer Tools to Debug your Webpages
Thanks
Best Regards
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