There are some chapters that don't even download for me.
x265
Your Country, Selection, Settings and SF version are unknown ..
.. so it's complete useless for me to test anything
Name the requested infos or better:
Close SF, rename the StreamFab.log
start SF, try once and after fails close SF
and attach your new StreamFab.log to your post
btw: I think your problem has nothing todo, with "Unlisted SF 6240 changes" ..
.. so please open a new topic for your problem - thanks