After sync HD TB with NAS, comes an ERROR "Thunderbird is already running, but is not responding.To open a new window, you ..."

Hallo,
i need Help again...
I´d sync my Fritz.box Disk (User Doc´s and TB) with our new qnap-. NAS- Disk.
After then, if i start one of the Thunderbird´s from the Fritz.Box (NAS) Disk coming ever the ERROR
"Thunderbird is already running, but is not responding. To open a new window, you must first stop the existing Thunderbird process or restart your computer."
original in Germany "Thunderbird wird bereits ausgeführt, reagiert aber nicht. Um ein neues Fenster öffnen zu können, müssen Sie zuerst den bestehenden Thunderbird-Prozess beenden oder Ihren Computer neu starten."

But is the only running instance, at this Moments.
The copy on qnap- NAS is running without Problems.
Finally, I copied from qnap-NAS-disk to PC- connected Fritz.Nas- disk back the entire Thunderbirds portable Directorys. > The same ERROR at starting by 3 profiles. in Win 7 Ulti and Win 10 Pro

greatings
bodobob