Hello there,
Thank you for reaching out and for the screenshot.
We understand some newly acquired enhancement cores didn't stack with some older ones you have. This does seem strange to us. For our investigation, could you kindly let us know if you received 45 cores when that stack was at 971? Also, did the newer cores from a different source than the older ones? Once we know these details, we'll review.
I don't remember. I suspect it's because some of the enhancement cores came from the postmaster, so they didn't stack. Since I've now obtained more enhancement cores, the stack has been filled up, making it impossible to verify.
No idea what causes this but can confirm I have seen it happen from time to time.
Sometimes cores just seem to make a new stack or arbitrarily split rather than fill a full stack or merging with an existing incomplete one.
I have found moving a stack or three back and forth between inventory and the vault a few times usually gets them to recombine.