P: Slideshow preset quality not saved correctly

hi
there is a bug lightroom 6.8cc & 6.9cc in the slideshow module
it doesn't keep the slideshow ,quality settings

i tried to create a preset with all settings and set it as default
in short i start lightroom 6.8 and i have tried with 6.9 , change the slideshow quality to draft or high
when i close lightroom v6.8cc and 6.9cc ,and I restard lightroom the preferences are restored to standard

i tried to ask to the forum but nobody answered https://forums.adobe.com/thread/2288964

windows 10 pro 64bit , lightroom cc last update 2015.9 or 6.9cc (but the issue was present in 6.8 too)
can somebody confirm it ? or is my system the problem?
thanks
best regards