Is it safe to defragment an HDD with plots on it?

[MrR341-GER]

I recently plottet 6 Plots on my HDD, but I'm using it for other things as well...
And it was a mess... I had 93% fragmentation and did an defrag... Now I'm back to healthy 6% fragmentation, but as soon as I start chia, the plots keep up ending in a "Synching"-Loop... or rather It seems so...

What can I do now?

EDIT:
It's farming again but the 5 Months increased to 7 Months... Do I have to stayed connected?