After collecting 100 cells and then collecting 5 cores and upon using the Reassembly machine, it states that Zygarde 50% with Power Construct will be made. Upon click the confirmation button, I'm given Zygarde with Aura Break. I assumed this was due to Power Construct being a hidden ability, but upon Zygarde getting injured below half-health. Power Construct doesn't activate. Going into the Poke editor shows that Power Construct is unavailable to choose and aura break is the only option. After talking with someone about it, I was suggested to make a ticket

Thank you for posting, but I am not able to reproduce this bug in the latest version. If you are still experiencing this bug in the latest version, feel free to make another ticket.