Can you précise a bit the side effects of reseting the prefs, please ?
I have thought to reset the parameters, since it's possible from the preference menu, but I always fear unexpected side effects, and I like to be able to weight the cost compared to the interest.
E.g: will the directory path of the backup of the catalog be altered?
What other consequence may I fear?
A few others have reported this problem in the official Adobe feedback forum: Lightroom 6.0.1 clears filter during export. Please add your vote, details of your issue, and whether or not resetting preferences worked to that topic. Best to continue the discussion there, since that will help the others experiencing this problem.