I like AIM solder paste, personally. But, much like asking which pick and place machine is best on this board, you're likely to get as many opinions as there are paste manufacturers.
I just took a look at Alpha's datasheet for this product, and it seems like a standard paste. It's got a shelf life of 2 weeks at room temperature, as do a lot of other pastes. Given this, I wouldn't expect significant drying in 15 minute cycle times.
A couple of things to check: 1. The operating environment like for the stencil printing? Temp/Humidity/air flow. 2. Temperature of the paste at the beginning of operations (warmed up to room temp per vendor recommendations?). 3. Aperture design of stencil. 4. Age/storage conditions of the solder paste. 5. Appropriate sphere size for aperture design/application.
It might be worth getting the paste rep/application engineers involved in helping you diagnose the root cause of your issue. They have the most knowledge about the paste product you're using, and can analyze your process with their product to determine the causes and potential solutions.
Cheers, ..rob
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