1 draw on the chromatic

I seem to have tamed the difficult draws on diatonic harmonicas (2 on G and A, 1 on C and D). It was hard to get a good tone for the 1 draw on the chromatic, but I got it.

Now, there remains an annoying small delay for 1 draw to respond.

At first I thought it was related to the tone problem, and that opening the throat / lowering the tongue better was the key to both better tone and timing. Then I had doubts, since draws are ok now on the diatonics I own.

As a test, I have tried to draw with the nose open (which used to "solve" wrongly the tone problem)... and it also "solves" the delay problem... so this is indeed related.

What bothers me is that I feel I am progressing everywhere else (bending included)... but for months I seem to make no progress on the chromatic 1 draw. I still cannot play No Sweat up to the end, because this small delay makes tongue-switching too tiring (and No Sweat has a lot of tongue-switching).

Maybe I should tackle that differently, and come back to the chromatic later. Maybe if I try to solve another related problem, I'll have new ideas to try.

So this is my question: since my throat/tongue position is still flawed but the usual 1 and 2 draws come clear enough, how to let the problem appear on a diatonic?

Are there specific exercises that will fail because of this flaw?

Or maybe, are some low-key harmonicas more challenging for some draws?