Popup doesn't show with anchor tag

I have a popup that’s triggered by clicking a button, using a CSS class. When the popup text contains only heading and paragraph tags then the popup shows correctly.

When I add an anchor tag to the text, the popup no longer shows when I click on the button.

I have tested multiple times. Whenever I remove the anchor tag, the popup is
displayed. When I add the anchor tag back in, the popup doesn’t display.

The code for the popup text is:

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