What is the temperature in your shop when you are gluing?
BSI 15 minute recommends above 65 degrees.
The 30 minute recommends above 70 degrees.
The 5 minute is the most forgiving. They say it will cure down to 40 degrees.
Just a thought. You are just a little bit south of me, and my garage shop gets pretty chilly right now. But I have no idea where your shop is, or if it's climate controlled, so take it for what it is worth.
Bill