I made sure to restart my game, joined a game, and did everything I could to make sure it wasn't just me but It seems in customization the equipment tab for both insurgents and security when you try to select a camouflage for the light backpack or the heavy backpack they change the camouflage for the vest instead
[Deleted old screenshot link as it was irrelevant]
Looked into it a little more, seems like selecting either the heavy backpack or the light backpack will show the camouflages you have unlocked for those backpacks, but when you try to select a camouflage for the backpack it selects everything in the equipment tab and only changes the vest.