Laptop: XPS 15 9570
BIOS Information
	Vendor: Dell Inc.
	Version: 1.15.0
	Release Date: 12/25/2019

Ubuntu 20.04 LTS
Uname: 5.4.0-29-generic #33-Ubuntu SMP Wed Apr 29 14:32:27 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux

TB16 with latest firmware (3 jan 2019)

Fully reproducible:
When the "User Authorization" Thunderbolt security feature is enabled, USB devices plugged in to the TB16 randomly disconnect. 
When "No security" is set, this does not happen.


Log:
May  6 20:34:55 user-XPS-15-9570 kernel: [  657.090759] usb 5-1.4.4: USB disconnect, device number 30
May  6 20:34:55 user-XPS-15-9570 acpid: input device has been disconnected, fd 25
May  6 20:34:55 user-XPS-15-9570 acpid: input device has been disconnected, fd 27
May  6 20:34:55 user-XPS-15-9570 kernel: [  657.579631] usb 5-1.4.4: new full-speed USB device number 31 using xhci_hcd
May  6 20:34:55 user-XPS-15-9570 kernel: [  657.720769] usb 5-1.4.4: New USB device found, idVendor=24f0, idProduct=0140, bcdDevice= 1.00
May  6 20:34:55 user-XPS-15-9570 kernel: [  657.720774] usb 5-1.4.4: New USB device strings: Mfr=1, Product=2, SerialNumber=0
May  6 20:34:55 user-XPS-15-9570 kernel: [  657.720778] usb 5-1.4.4: Product: Das Keyboard
May  6 20:34:55 user-XPS-15-9570 kernel: [  657.720781] usb 5-1.4.4: Manufacturer: Metadot - Das Keyboard
May  6 20:34:55 user-XPS-15-9570 kernel: [  657.730571] input: Metadot - Das Keyboard Das Keyboard as /devices/pci0000:00/0000:00:1b.0/0000:02:00.0/0000:03:01.0/0000:05:00.0/0000:06:04.0/0000:08:00.0/0000:09:01.0/0000:0a:00.0/usb5/5-1/5-1.4/5-1.4.4/5-1.4.4:1.0/0003:24F0:0140.0036/input/input109
May  6 20:34:55 user-XPS-15-9570 kernel: [  657.788516] hid-generic 0003:24F0:0140.0036: input,hidraw5: USB HID v1.10 Keyboard [Metadot - Das Keyboard Das Keyboard] on usb-0000:0a:00.0-1.4.4/input0
May  6 20:34:55 user-XPS-15-9570 kernel: [  657.790664] input: Metadot - Das Keyboard Das Keyboard System Control as /devices/pci0000:00/0000:00:1b.0/0000:02:00.0/0000:03:01.0/0000:05:00.0/0000:06:04.0/0000:08:00.0/0000:09:01.0/0000:0a:00.0/usb5/5-1/5-1.4/5-1.4.4/5-1.4.4:1.1/0003:24F0:0140.0037/input/input110
May  6 20:34:55 user-XPS-15-9570 kernel: [  657.848086] input: Metadot - Das Keyboard Das Keyboard Consumer Control as /devices/pci0000:00/0000:00:1b.0/0000:02:00.0/0000:03:01.0/0000:05:00.0/0000:06:04.0/0000:08:00.0/0000:09:01.0/0000:0a:00.0/usb5/5-1/5-1.4/5-1.4.4/5-1.4.4:1.1/0003:24F0:0140.0037/input/input111
May  6 20:34:55 user-XPS-15-9570 kernel: [  657.848589] hid-generic 0003:24F0:0140.0037: input,hidraw6: USB HID v1.10 Device [Metadot - Das Keyboard Das Keyboard] on usb-0000:0a:00.0-1.4.4/input1
May  6 20:34:55 user-XPS-15-9570 mtp-probe: checking bus 5, device 31: "/sys/devices/pci0000:00/0000:00:1b.0/0000:02:00.0/0000:03:01.0/0000:05:00.0/0000:06:04.0/0000:08:00.0/0000:09:01.0/0000:0a:00.0/usb5/5-1/5-1.4/5-1.4.4"
May  6 20:34:55 user-XPS-15-9570 mtp-probe: bus: 5, device: 31 was not an MTP device
May  6 20:34:56 user-XPS-15-9570 boltd[1432]: probing: started [1000]
May  6 20:34:56 user-XPS-15-9570 mtp-probe: checking bus 5, device 31: "/sys/devices/pci0000:00/0000:00:1b.0/0000:02:00.0/0000:03:01.0/0000:05:00.0/0000:06:04.0/0000:08:00.0/0000:09:01.0/0000:0a:00.0/usb5/5-1/5-1.4/5-1.4.4"
May  6 20:34:56 user-XPS-15-9570 mtp-probe: bus: 5, device: 31 was not an MTP device
May  6 20:34:59 user-XPS-15-9570 boltd[1432]: probing: timeout, done: [2907295] (2000000)