Most probably a CodeBlocks linked against wxWidgets >= 3.0, not sure if it only happens on Windows 10, but i have the same issue with my CodeBlocks with wxWidgets 3.1.2+, but i can live with that
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Its sort of funny, it happens only on the notebook tabs, not only the ones of the editor pane, but the tabs in all panes like management, logs. If the mouse hovers on a tab the keyboard focus is lost, if the mouse leaves the tab it returns where it was. Seems to be a CodeBlocks issue because it doesn't happen in the AUI sample.