[Ver12.0.1.1(64Bit)] Deleting does not work

[RiseFly]

Your tasks are using two-way sync, two-way sync can not select the mirroring mode.
Instead, you can select the "Delete: Delete the remained files from the other side" option.

[3PO]

One-way is not "syncing", one-way is a simple backup and therefore i don't need a expensive App like "BestSync".

I cannot understand, why this don't work anymore, in a former Version (e.g. 2016) it worked fine.

[RiseFly]

As I said before, the two-way sync do can delete the remained files (files deleted from the other side) "FROM" the "LAST" synchronization.
If you setup a new task, at the first time of synchronization, the task can not determine whether a file is added or deleted from any side.