Ultimate fade-in slideshow no longer responsive in firefox version 80 and later

1) Script Title: Ultimate fade-in Slideshow (v2.6.1)

2) Script URL (on DD): http://www.dynamicdrive.com/dynamici...htm#dimensions

3) Describe problem: Pages with this slideshow are no longer responsive in Firefox version 80 and later. Same for later versions of Chrome and Opera.

I use this on my site on some pages, for example, dpflutes.com/index.html
This is no longer responsive but pages without the slideshow for example dpflutes.com/contact.html are OK and respond fine to screen size.

This has not been an issue on firefox 79 and previous versions
I cannot work out why this is a problem. Any help or advice on how to get it responsive ln these newer browser versions would be appreciated.
Thanks in advance,
Daniel

PS I should add that this applies to Firefox, Chrome and Opera on an android phone. I assume that it is the same on other small devices but I can't test on them.
Thanks in advance,
Daniel