Windows 10: Lenovo t450s - strange behaviour, no clue at all!

Good morning, since some time my beloved t450s started to act like crazy https://imgur.com/a/uJJoaUS. At random moments doesn't matter what I'm doing screen flashes and then take me back to the desktop BUT with a black rectangle that prevents me doing almost anything. At first I thought was the old SSD maybe some failure or bad sector, so I've changed it with a new and a bigger one but the problem persist. What could be the cause of this annoying thing? Thank you in advance :

:)

 

Convert SSD from MBR to GPT on Lenovo T450S laptop

To understand better what you have, please post a Disk Manager image (full window, expanded columns).
How to Post a Screenshot of Disk Management


The M.2 drive was used as a disk cache. With a SSD it is quite useless.

There is a new BIOS for the T450. Suggest you update it.
BIOS Update (Utility & Bootable CD) for Windows 10 (64-bit), 8.1, 7 (32-bit, 64-bit) - ThinkPad T450, T450s - Lenovo Support GB

 

Convert SSD from MBR to GPT on Lenovo T450S laptop

 

windows 10 on lenovo t450 and bluetooth

Running windows 10 on Lenovo T450. Using Intel Bluetooth driver 17.1.1529.1620. Chipset, bios etc. have been updated using Lenovo's support site.

I was able to initially add Microsoft designer mouse using Bluetooth settings. However, after computer goes to sleep, mouse is no longer working. And, it is not a simple matter of unpair and pair back to get it working with laptop again. Sometimes Bluetooth
will see it as a device ready to pair and sometimes it wont.

This mouse was rock solid on Windows 7.