Random freezes on Precision 5540 that came with Ubuntu 18.04

Had it for under 3 weeks so far but my laptop has locked up over five times now.
It does it randomly, like when starting up (one of the five loading dots orange), or using the touch screen while using Chrome or rotating a view in Blender with just the default cube.
Don't know why it does that or how to reproduce it.
Couldn't find anything in the logs (BIOS, kern.log, syslog).
Still froze once even after reimaging via a USB I created via Dell Recovery.
Once froze during a Skype call, in which the sound was skipping like a CD.

System BIOS has been upgraded to 1.9.1.
Ran Diagnostics (Pre-Boot System Performance Check 4400.13) twice, but with no errors.

I tried chatting with a Live Agent via WhatsApp, but he referred me here because his support is primarily with Windows, and that he assures me that no hardware issues are present as the diagnostics have passed.

Here's the output of `fwupdmgr get-devices`:

Precision 5540 Thunderbolt Controller
DeviceId: f9296f41259e7d753e918056164777ac2cd49b8e
Guid: 42598a87-0ee2-5d7e-b1d1-02a312041fd5 <- TBT-00d40906-native
Summary: Unmatched performance for high-speed I/O
Plugin: thunderbolt
Flags: internal|updatable|require-ac|registered
Vendor: Dell
VendorId: TBT:0x00D4
Version: 44.00
VersionFormat: pair
Icon: computer
Created: 2021-03-05

Precision 5540 System Firmware
DeviceId: 90dce4a3c3eb770c96eaa7fa7f45e984fc66206d
Guid: 417d4c2a-87d1-4d7c-bcea-322041f2d5a3
Plugin: uefi
Flags: internal|updatable|require-ac|supported|registered|needs-reboot
Version: 0.1.9.1
VersionLowest: 0.1.9.1
VersionFormat: quad
Icon: computer
Created: 2021-03-05

Precision 5540 TPM 2.0
DeviceId: c473de1ae11b072f36cd71aaeac6a445627f4687
Guid: 0584e003-d9d2-5b8d-866f-20a2d59bc7ad
Summary: Platform TPM device
Plugin: uefi
Flags: internal|updatable|require-ac|registered|needs-reboot
Vendor: Dell Inc.
Version: 7.2.0.2
VersionFormat: quad
Icon: computer
Created: 2021-03-05

PC711 NVMe SK hynix 512GB
DeviceId: f2759da7fe8e0388c5f3601cb072f837b1070b03
Guid: d1294b62-34ff-5b5b-a5c9-7ac4cba4d398 <- STORAGE-DELL-110003
Guid: 43971f62-88f2-11ea-bc55-0242ac130003
Serial: CN0CN64751260CH2I
Summary: NVM Express Solid State Drive
Plugin: nvme
Flags: internal|updatable|require-ac|registered|needs-reboot|no-auto-instance-ids
VendorId: NVME:0x1C5C
Version: 41001131
VersionFormat: plain
Icon: drive-harddisk
Created: 2021-03-05