Alt+dragging keys is a shortcut for the Shift tool.
But it looks like Alt-dragging a clear space in the dopesheet was recently made a shortcut for panning the dopesheet.
Now when you try to alt-drag keys, your cursor inevitably lands on clear space on the dopesheet, so it ends up panning instead of shifting keys.
Repro steps:
(0) Open an animation with a good set of keys.
(1) Hold alt + drag one of the first keys to the right.
Pans when the cursor lands on a clear space.
