Suppose $(M, g)$ is an open complete nonnegatively curved Riemannian manifold with $d$ its distance.

A totally convex set $C\subset M$ has the property that for any two point $x, y \in C$ *any* geodesic (not only the minimal ones) joining them must lie in $C$.

If $C$ is totally convex, the fattened set $C^a=\{x \in M \mid d(x,C)\leq a\}$ is still totally convex? Is it at least for small $a$?

This question is somehow related to question "Examples on small cut radius of totally convex set in non-negatively curved manifold", Examples on small cut radius of totally convex set in non-negatively curved manifold