I'm not convinced the bug is in the add-on. TBKeys-lite worked perfectly well under 1.15, and only causes issues with the Quicksearch window. Given the number of other bugs reported against the quicksearch window, this looks more like a bug in quicksearch.
Bug 1908233 Comment 9 Edit History
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I'm not convinced the bug is in the add-on. TBKeys-lite worked perfectly well under 1.15, and only causes issues with the Quicksearch window. Given the number of other bugs reported against quicksearch in 128, this looks more like a bug in quicksearch.