UM 18.04.2 logs out instead of suspend and destroys unsaved documents

I just installed Ubuntu Mate 18.04.2 in a new laptop (HP 15-da0xxx, i5-8250U, 8GB RAM, NVIDIA GeForce MX110).

For a couple of weeks, I had Linux Mint Cinnamon 19.2 (therefore, kernel 4.15.0-46); but as I am more used to Ubuntu Mate, I installed UM 18.04.2 (kernel 4.18.0-16).

The problem I have is that when I suspend the machine it doesn't really suspends, but logs out, so open unsaved documents are lost (which didn't happen with LM Cinnamon).

I just tried with my old Samsung laptop (UM 18.04.2, up to date, but no HWE, so kernel 4.15.0-46, 4 GB RAM, no graphics card) and it works as expected: after suspending the machine, I wake it up and the unsaved documents are there.

Thanks in advance for your help.

Axel

[This is already partially solved, but I didn't know how to marked so.]

First, I should have said “... when I suspend the machine it logs out and suspends, so open unsaved documents are lost .”

Now ---thinking about the difference between the two machines (old Samsung, UM 18.04.2, but with kernel 4.15, no graphics card) and the new one (HP with new ISO image of UM 18.04.2, so kernel 4.18, NVIDIA graphics card), I realized that, besides the kernel, the main difference was the graphics card...

So I switched to Intel GPU... and problem gone! I could leave an unsaved document when suspending the machine and, when waking it up, the document was there. Then I tried using the NVIDIA card with the Nouveau driver instead of the NVIDIA proprietary driver, and also no problem at all! So it was the NVIDIA 390 driver!

I will wait for a new version of the driver and try again, but for now I can use the GeForce MX110 with the Nouveau driver.

Best regards,

Axel