Here is a good post on solving that issue.
Mine has been working after I:
Added rubber bands to keep constant downward pressure on the router.
Looked for highspots in the inside of the router base. Especially in the channel where the bead on the router lines up. File this down slightly
Loosen the router base clamp just enough so the router slides freely but does not have a lot of slop.
Wax the the router where it slides in the base.
Don’t give up on it, it gets better after you work out a few kinks