The shaker you have in hand may be a rare defect, but sometimes it's a known issue of all capped stainless steel shakers as they tend to get hard to remove after shaking due to the condensation of the stainless steel. Luckily, there are some cool quick fixes videos:
1. How to free a jammed/stuck shaker top part (strainer part)?
https://www.youtube.com/watch?v=8aK3RuQeZ74
2. How to free a jammed/stuck shaker cap?
https://www.youtube.com/watch?v=IWvRuGrxuSA
We would love to hear what worked for you and of course, If you still have issues with the shaker, please write to me with your Amazon order ID (or complete shipping information), and we will be providing you with options.