Nextcloud Sync Client on MacOS errase without permission on my local drive

Hello everyone.

I have a big issue on my Mac.
I was on macOS Mojave until end of March 2020 and I’m on macOS Catalina (10.15.4) now.
I’m using Nextcloud Desktop Sync. (V2.6.4stable) - build 20200303

Since january 2020, i have trouble with the sync. between my server and my Mac.
After connecting all my file from my local drive folder (Nextcloud), each of my files are sent to my distant server web. Which is good and all my files are accounted for.

However, i discovered the first time in January (i was under macOS Mojave) that a big part of my files where gone on my local drive.
I checked on my distant drive, and all of them where still on my distant one.

So i disconnected my account on Nextcloud Sync on my Mac and reconnected it, to load again all my files to my local drive.

It took times, but after some weeks one again, my files where gone again from my local drive. (still available on my distant drive - fortunately)

I re-did a sync between my distant and local drive and my files stayed on my local drive for a long time until end of march before my upgrade to macOS Catalina.

After discussing with a friend of mine, i decided to upgrade my OS with the hope to solve this issue (loss of my local files).

Unfortunately, it did not work at all and i had to disconnect definitively Nextcloud Sync to keep my local files on my local drive.

Did anyone has the same issue ?
Did anyone has a solution ?

Thanks for your reply.