yup, i had a Gigabyte Mobo once, that i bought with 2 kits of 2x8gb RAM. They were the same make and same spec, but they just would not work together.
By moving them around and trying them in different slots, i discounted any chance of a dodgy stick(s) or RAM slots on the Mobo.
The supplier told me i should have bought 1 kit of 4 sticks.
nm, i just used 2 and my son made use of the other 2 sticks. We later found out that his mobo wouldn’t take both sets either. It might have been an issue with having all 4 slots occupied, rather than a RAM timing issue, but i suspect the issue has now been designed out of mobos.