@Matt_Hartley as per my previous update, it looks like this was a mobo issue. Nearly 2 months later now with the new mobo and it all works perfectly with no issues. Do you think it’s worth marking this as resolved?
As for the ucsi_acpi error messages, just to give a final answer to @Nimrod_Hajaj as well, they appear to have been unrelated and have been resolved with the BIOS 3.05 update (also included in the ChangeLog). I’ve not seen them since I updated. In fact, my dmesg output is devoid of any errors, unlike my old ThinkPad which the FW13 replaced 