Same issue with the rx 5700 xt nitro se on an asus prime x570 pro.
Sapphire nitro rx 5700 xt special edition rgb cable.
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In this video we go over adjusting led lighting on sapphire radeon nitro rx 5700 xt 8gb oc and more.
Brand new windows install with latest drivers software.
In this video we go over how to change lighting on sapphire nitro rx 5700 xt sapphire trixx.
If i switch nitro glow to external source the card s lights just get stuck on whatever pattern was showing before.
Check out the card on my amazon affiliated link.