For as long as I have played PUBG I have never been able to game with an overclocked ram frequency or even super tight timings.
But I have finally worked out what was causing the crashes.

In the UEFI Bios screen, go to the part where you adjust LLC and phase control, things like that (forget the name but it's there.
PUT YOUR DRAM CURRENT CAPACITY UP. I went 130% and it's probably going to be ok depends on the voltage and setting you use.
setting this to 100% will cause the ram to shut off when it reaches 100% , that's what was giving me crashes in games.
1700 is very good at 3.8ghz with a lowish voltage and fast ram, fans aren't sup[er loud and it gets nice 60-110 fps 3440x1440.
this is with the ram settings in the ram setting list built into the bios.