Mistake "can not delete "sync.ffs_db file". Sync works but logs say "mistakes".

[Vlad]

Hello everyone!
I have two VPS at amazon (win server 2012 r2) and I'm trying to sync some files between them "two ways". I do it by meens of Schedule a Batch Job creating tasks in Windows Task Scheduler (like here https://freefilesync.org/manual.php?topic=run-as-service). And it WORKS, but in logs it indicates a mistake
"Can not delete file "sftp://_._._._/IIS/sync.ffs_db.
Mistake code LIBSSH2_ERROR_SFTP_PROTOCOL: SFTP Protocol Error LIBSSH2_FX_PERMISSION_DENIED (libssh2_sftp_unlink)". (By _._._._ I meen my real IP).

I can not understand why it wants to delete "sync.ffs_db" at all. But even when I delete it manually it appears again after syncing and the same mistake in logs again.
As I said, sync WORKS. But only when "handle errors" is set to "ignore" (item 1 on the same page https://freefilesync.org/manual.php?topic=run-as-service). If I choose it "pope up" it'll stop with the pope up and if I close it sync will not be complete. Of couse it's not a big deal and I check the box "ignore", but it's not good to have all the logs declaring mistakes and check each time if the syng was correct.

[Zenju]

Updating this file consists of multiple steps: 1. create temporary, 2. delete sync.ffs_db 3. rename temporary.

[Vlad]

So what should I do to avoid "mistakes" in logs?
It is interesting, that when I do the same sync at the same computer (not through SFTP) - it works without any mistakes. Something takes place when it's remote. I tried playing with number of "SSH connection for directory reading" and "SFTP chanels per connection" (trying "1" or "2" each) - it didn't help.

[Zenju]

The error is a real problem and should be fixed, e.g. make sure FFS has permissions to delete sync.ffs_db.

[Vlad]

Where I can check FFS for permitions? Sorry, I'm not a big expert...

[Vlad]

Zenju
If it helps to fix it trowgh TeamViewer, I'm ready.

[Vlad]

As I played with that here's what I found.
1. Concerning"...make sure FFS has permissions to delete sync.ffs_db.". Somehow only sync.ffs_db file can not be deleted. Any other files deleted from computer A delete from computer B when syncing - no problem. Of cause I had to switch to mirror mode since "two way" is delicate with deleting files, but the main idea is that NOTHING prevented files from been deleted if I wanted so. Which means that FFS has permissions to delete files.
2. When I deleted sync.ffs_db file manually and synced needed files in MIRROR mode, no new sync.ffs_db file appeared, no any errors in log files. Everything is perfect. When I delete any file in computer A it deletes that file in comp B.
So had I used Mirror mode I'd be totally satisfied. But I need "two ways". As soon as I switch to "Two ways" the error messages in logs start. As I said earlier it only happens when remote syncing (the same operation within computer A doesn't indicate any errors).
So any ideas, please.

[Vlad]

I still have the problem. If updating this file consists of multiple steps: (1. create temporary, 2. delete sync.ffs_db 3. rename temporary) - could the problem be the delay between the computers? The ping is 200ms. Are there any settings in FFS to adjust to the delay?
Thanks.