Stanislaw Gruszka [off-list ref] writes:

Hence looks like forcing firmware upload somehow changed device, now it
is capable to initialize. On my second system device is on pristine state
and original problem is still reproducible. Do you have good solution
for this problem ?

Did you see this:

mwifiex: fix racing condition when downloading firmware

https://patchwork.kernel.org/patch/9123771/

Though I have no idea if it helps in your case, just saw it on my queue
of patches to apply.

-- 
Kalle Valo