I have used dokuwiki for many years but recently certain pages within my wiki have started to load very slowly and whilst these pages are loading it slows down other pages if people are trying to access them. It seems to happen on pages containing images but not all pages with images. The problem images are not even large files.
On particular page that is a problem hasn't changed for years but whilst it used to load ok it now is very slow (perhaps taking around 60s to finish loading). The page is visible but does not respond if links are clicked etc. Some images can take a long time to show.
Using the site https://www.debugbear.com/ I see that some image elements do take a long time to load using the fetch.php command. Three in particular show durations of 30.9, 91.3 and 61.1s
I was using Greebo but have made a copy of the wiki and updated to Igor but this made no difference. I have also tried disabling all plugins but again this had no effect.
Any ideas on how to investigate further/resolve?