By select you have to select links as you select text in a web page (click and dragging and then right-click somewhere)

If you can share in which page please do it here or via email to the support email open.links.in.tabs@gmail.com

This was created specifically to Firefox 57 as an extension I had was not compatible and I use it daily without problems since

Edit: Tried it multiple times (for instance in https://bouldersintra.wordpress.com/2017/11/02/um-verao-excessivamente-quente/ ) and could not replicate it.

Can you provide an address and what was selected. Thanks for the feedback!