Watch out for that new quick-set mortar mix from the big box store

I was on a chimney repair job in Chattanooga about six weeks ago. The homeowner wanted it done fast, so I grabbed a bag of that 'Rapid-Set Pro' stuff. It said 30 minute working time, which should have been fine. I mixed a small batch to reset about twenty bricks. The stuff went from wet to rock hard in maybe 15 minutes. I barely got the last three bricks in place before my trowel was scraping on what felt like concrete. One of the bricks wasn't seated right and I couldn't adjust it at all. I had to chip it all out and start over, wasting a full bag and half a morning. The label is a flat out lie. Has anyone found a reliable fast-set mix that actually gives you the time it says?