Whenever you're in the creative inventory, not the search tab, pressing any key will send you to the search tab. For the most part this is expected, but pressing ESC or whatever key you have bound to [Inventory] should close the inventory, not try to search.
This was not an issue in 1.10, but I don't know what 1.11 snapshot it started in.
This issue has suddenly stopped, and I am unable to reproduce the issue. I suspect there's another factor at play here.