My Safari's JavaScript seems to have a problem. How can I reinstall it?

Hi,

I've recently just updated my macOS to High Sierra version 10.13.6, and Safari to version 13.1 (13609.1.20.111.8).

Since then, I've encountered problems with a number of websites where I keep getting this error:

"A problem repeatedly occurred with "[website URL]"

Example 1:

Example 2:

I realize that the problem goes away when I disable JavaScript.

How can I fix this issue and re-enable JavaScript again?

It seems very difficult to downgrade or reinstall my Safari.