Try enabling XMP, then set it to 2933, then change the voltage to 1.39v
You have a gigabyte board and while gigabyte isn’t a bad mob brand, their bios QA is somewhat lacking
Often xmp will not change voltage automatically and manually changing bios doesn’t do anything the first time, you’ll want to try setting and saving changes multiple times
The reason why you’re probably having problems is you have it set to 1.25v when it’s a 1.35v kit
See if that’s stable then we can try 2 things, first trying to get that kit to 3200mhz, which may or may not be possible depending on the silicon quality of your particular 2600
If we can’t get 3200 then we’ll work on lowering the timings to say 16-16-16-32
Also check and see if you can get command rate to 1