T7500 failed sleep

Hello

I picked up a T7500. I have windows 10 on it and for the most part its great. However come sleep time something is going wrong, the numbers 3 and 4 light up which would suggest its gone to sleep, however the power button is not flashing its solid. From here you cannot use the machine until a hard power off.

Its not asleep, fans are still going, but it has frozen. 

I suppose I could just prevent it from sleeping, but I would prefer to fix the issue. It could be windows. I have a faair amount of dell machines in the house all the rest sleep just fine. Or even if they dont sleep fine, they have not crashed.

Any ideas on how I can diagnose?

I have not sat and watched it all go wrong, its just how it is in the morning. I wouldn't be surprised if it successfully sleeps for like a minute then wakes its self back up. People usually suggest to disable wake on the network interface, but really thats something I want!

Cheers