This issue is because an antivirus software like windows defender checking through the file every time the UCCNC writes a key and especially if your computer has slow hard disk access this can slow down the saving process a lot.
We changed the saving method in the UCCNC a few versions back to avoid this issue. The new saving method doing the Save all keys into memory first and then flushing it to the file with a single write cycle, so antiviruses will only check the file once.
Also we've added protection to not let do anything like button presses while saving is ongoing.
It is yet in the test release only though, which you can download from here (1.2047 is the latest test release version):
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