either delete left or delete right does not work if the respective drive is a network drive (or usb stick??).
It seems that TC is trying to delete into the paperbasket which will not work.
Answer in the german forum from Mr Ghisler (Author):
Thanks for the hint, I will examine this. You can work around this by holding down the Shift key while clicking on the "Sync" button. Then the trash is bypassed.
Fixed in TC 9.0 Beta 5
> Synchronizing with USB stick (and deleting files) without error message possible
> Right-click and -> delete right/left in synchronization window again without error message possible
