WIth bios version 1.5.1 installed you cannot restart windows 10 when a device is attached to USB-C port.
The computer will start with dell diagnostic screen and give error hardrive not installed. When you enter the bios, no harddisk is listed. Turn off/on device, no issues. Only on a reboot.
When removing thunderbolt device (tried both TB16 docking and LAN adapter) no issues.
Went back to bios 1.4.0 issue solved.
W10 enterprise. Bitlocker active. Secureboot on. Sata mode AHCI. TB set to no security level. ThunderboltAdapter Boot Support disabled.
Also option "Enable Attempts legacy Boot" is grayed out and enabled. Cannot disable it.