Unfortunately it looks as if i will have to wait for GL.iNet to fix all the new firmware I had this issue before Here is one of my posts.
The problem was fixed on firmware 4.4.5 for the GL-AX1800 Flint & GL-AXT1800 Slate AX and others but the new GL-MT6000 Flint 2 never had the old firmware, if you check the the fixes for the 4.4.5 it doesn’t mention the fix I believe, but i was told by alzhao GL.iNet Staff Member.
One last and very important comment on my GL-AXT1800 Slate AX running firmware 4.4.6 exact same settings everything work 100% until I upgraded to firmware 4.5.0