Thanks for the involvement.
There's a way to fix the behavior you observe. From Tools->Options->Environment->Keyboard options page you can adjust VS & JustCode keyboard shortcut the way it suits you. If you type "JustCode" in the "Show commands containing:" text field, you'll get all JustCode commands with their keyboard shortcuts.The ones you're looking for are "JustCode.GotoNextError" and "JustCode.GotoPreviousError". When you select one of the commands you can customize its keyboard mapping. In our case you can just choose the shortcut you want to remove from the drop-down list ("Shortcuts for selected command:") and hit Remove. Then you'll need to assign a shortcut for the original VS commands which are "Edit.ScrollLineUp" and "Edit.ScrollLineDown". That should do the trick. In case at some point you want to use the original JustCode shortcuts you can do so by going to JustCode->Options->General options page and pressing the "Restore keyboard shortcuts" button on the top of the page, which will overwrite the VS settings and restore JustCode ones.
Let us know if that works for you.
the Telerik team