Hello otec
Yeah 2133MHz is default so 3733MHz is a huge overclock, as Praz says it will be up to the cpu's integrated memory controller if it can handle it and you're going to have to tweak voltages pretty good to have any chance of getting it there.
Try the Dram voltage at 1.40v - 1.425v
vccio voltage to 1.25v-1.30v
vccsa voltage to 1.30v - 1.35v
Raising the cpu input voltage to 1.90v might help, this is not the vcore, stock voltage should be around 1.80v. In DIGI+ try setting the Dram current capability as high as it will go which is 130% on my board.
If you can't get it to go try setting it manually sometimes this will help. You can select a lower frequency and work your way up. You can try maximus tweak mode 1 and 2 at the top of the timings page. You can also try with 8GB.
I'd like to see you hit that speed.
🙂