TvHeadend: Special user-rights for USB-access needed?


I have installed DietPi v6.26.3 successfully on a BananaPro with an USB-SSD added by DietPi-Driver-Manager. Samba is running fine reading and writing with a Windows-PC.

Then I’ve installed TvHeadend v4.2.8-36 with my USB-DVB-C-device successfully, and after configuration TV is running fine.
But I can’t perform any recordings although my USB-SSD is correctly mounted and has engough free space (95 of 200GB shown in TvHeadend-Mnu). The error-message is “File not created”. Does anyone know which special rights are there to be set for DietPi or TvHeadend?