In Safari 13 release notes it is stated that there is no longer the need to apply the following to an element to enable the bounce scroll effect:
div { overflow
I don't know if i really understand this correct, but here it goes! :)
Can't you just remove that line of code from your file?
You could also try to write -webkit-overflow-scrolling: auto; !important
-webkit-overflow-scrolling: auto; !important
Hope this helped :