Hi diminstor A,
Thanks for your post. Based on my research, fragmentation is the likely culprit, SSDs work off TRIM in which it's constantly reording the drives for optimal performance, regardless of data structures (partitions).
You can force a trim update.
The other thing that could have happened is that your OS files got moved around.
It could be that your paging system was part of the unused drive.
I'd start with a forced trim, don't use defrag, and then work through an elevated command prompt:
DISM /Online /Cleanup-Image /CheckHealth
This will force windows to verify the integrity of the file system and update anything that's not the way it should be.
Best Regards,
Ian Xue
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