I just had the same issue. The way to fix it is very simple once you find it :D!
Go to your 3D software and copy the UV map that you want to appear in UV Channel 0 first.
Once you do this delete the old UV channel. In your case try to copy the UVs in the order you want to appear in Unreal and again delete the old ones.
I know it is supper annoying but it worked for me, I hope it does work for you as well!
Regards
Stan