[stumped]

not as yet. my HDX tablet only went to 5.6 a day ago or so, but my new fire sticks came with that on board as did my new HD 10, I think. 5.6 has the greyed out install bug on sideloading. but it can be worked around. I am loading up versions of youtube on everything because of the latest amazon- google bust up which threatens to zap amazon versions on dec 31st.
I have watched both amazon & netflix in HD on the new fire sticks which obviously are wifi only ,& no drop outs or quality dips

its taken them ~3 years but I think they have finally gotten the fire stick design right- I must have bought and sold at least 4 of the previous generations, which would overheat and glitch. and at UK £25 in the black sale last week, what's not to like - I bought 2 ! . I just have to keep repeating the mantra " you do not need 4K- you will not be able to see the difference " until the desire to keep upgrading wears off.

wifi is such a pain to daignose e.g. I have a specific combo of 1 oldish dell laptop that will not work properly with one specific asus AP but works fine with router and with other APs, and works if I plus in a USB wifi to the laptop. but the bad pairing gives me speeds of 1 -3 when other methods give speeds of 50 - 100
it bugs me on principle cos I cant solve it. I can bypass it easily enough but that's not the point. If I have any amazon device wifi issues I will post back though.
my usual tools are go to fast.com on tablet browsers and go into the netflix app for a network check on the fire TV & sticks
does googling wireless dropouts fire OS 5.6 find anything