If you can select a group of photos that have this issue, turn on Auto Sync and click Off in the Lens Correction Upright area, and after the change has propagated to the group, turn off Auto Sync. That should reset the Upright function for the group of selected photos without affecting anything else with the photos.
AutoSync is turned on and off by the little switch beside the Sync button in the LR Develop panel.
big thanks. bob