thanks for the key information (local ssd, ntfs compression)
i can not reproduce this delay on my ssd (non compressed folder, appx. 50mb file) using a 32 bit version of np++ 7.5.6.
could you try to temporarily adjust some np++ settings to try out if it makes any difference ?
settings > preferences > backup >>>
disable following options:
remember current session for next launch
enable session snapshot and periodic backup
backup on save > none