Insert Link button produces no dialog & removes scrollbar

I *was* using an earlier release than 4.2.2, upgraded to 4.2.2 to see if that fixed the issue, and it didn’t. I’ve confirmed this bug exists using 2 different themes (Default and 2014) in Chrome, Safari, and Firefox.

When I’m editing a post, and I highlight a word and then click the ‘insert link’ button in the toolbar of the editor, the only obvious thing that happens in the browser at all is that the scroll bar on the page disappears. No dialogs appear, no messages appear, no formatting changes…. nothing. Just the scroll bar goes away.

What are my options here? I didn’t see this listed in ‘known issues’. The only posting I’ve seen about it is here https://www.ads-software.com/support/topic/scrollbar-is-freezing-in-insert-link-window – but that was a year ago, and some of those suggested fixes I’ve tried, and others seem like stuff I shouldn’t have to do speculatively “just in case” like rebooting Windows or something (I’m on Yosemite, btw).

Is this a known issue, and is there a workaround or fix for it?
thanks.