I noticed this scenario and think it would be useful for others if turndown would handle this better.

Background:
( and ) are valid characters in a URL, and won't get escaped in normal HTML.
In markdown, links are surrounded by ( and ), if your link needs to have ( and ) you will need to escape them with \

For this input html:

<a href="https://google.com/file(1).jpg">link</a>

A valid markdown should be:

[link](https://google.com\(1\).jpg)

However turndown returns:

[link](https://google.com(1).jpg)

I'm now pre-fixing image and links in my html prior to calling the turndown service, but I really think this should be handled in the parser.
When you do, be sure not to double-escape URLs if there were already escaped (meaning, if the URL has "(1).jpg" there is no need to double-escape it.