In the recent LTS version of Ubuntu, if I right-click something the context menu immediately disappears after popping up, soI have to right-click again until, f

In the recent LTS version of Ubuntu, if I right-click something the context menu immediately disappears after popping up, soI have to right-click again until, for some unknown reason, it stays. I bet it's solvable, but I haven't bothered to solve it.