Using a timeline causes stutter/lag on the client

I had a similar stuttering issue with player crouching which I fixed by using a replicated variable to store the interpolated value.

I think your issue is the server and local player are both trying to do the same thing but there is a delay between the values. Maybe try setting the max walk speed using a replicated variable then only updating the replicated variable on the server and set replication condition to “skip owner”