You're most likely using the "modern" 384.59 driver with your GT610M in the 1503. Unfortunately this driver has buggy suspend support.
The only solution right now is to use the more reliable "legacy" 304.102 driver as your 1503 hardware is supported by both drivers (your 1501 can only use the "legacy" driver).
See this post for details on how to switch to the legacy driver. You're unlikely to notice any difference in image quality using the older driver.
Sorry, forum is screwing up the url by replacing "&" with "&".
If you're using the legacy driver and it still won't suspend that's quite unusual as the legacy driver works in most cases. Make sure your BIOS is up to date, that's the only other suggestion I have.
Hey!
I got it working. I reinstalled LibreElec and tried to "downgrade" to legacy drivers again exactly like I did last time, but now it worked great!
Why? I don't know, and frankly don't care right now as long as it's working. 
So, thanks guys!!
After reinstalling, did you try suspending before the "downgrade" to legacy? Could be just an addon that had a broken shutdown/suspend script that got wiped out when you reinstalled.
