This issue only seems to be happening on devices I use for work (not owned by me) so I might look into it at a later time but I probably won’t. In case anyone else has this same issue, what I ended up doing as a workaround is using the Customize Keyboard Shortcuts add-on.
In the config file, I ended up changing the values of window_browser reschedule and reviewer set due date from Ctrl+Shift+D to Ctrl+Shift+G.