Question 3 ram slots are present but gives off memory as if all 4 slots are populated

[Polo10101]

Hey guys, so i have 4x4gb ram sticks in all slots. It shows full 16gb but only 3 ram slots are coming up. The computer has been crashing a lot when it receives a bigger load such as gaming or even when watching videos. It has been doing all the other tasks fine like opening and typing on word documents etc. It gets me thinking whether it's the motherboard slot that's faulty or the ram itself. Any suggestions? Would like to be able to get it's full potential as I was considering starting some video editing but I don't think I will be able to do much if it crashes. It's just a very expensive office computer at this point :/

 

[popatim]

What is showing you only 3 ram slots?
Which motherboard do you have?

 

[Polo10101]

I've realised the fault in nzxt cam which showed only 3 ram sticks were detected and made me curious. I've entered bios to see if there's 16gb or 12gb and there was indeed 16gb. I've then entered cpuz which also said there's 16gb but only 3 ram sticks are detected and no data is shown on 4th slot.

The motherboard I'm using is an Asus z390 formula.