You should try re-calculating the toolpath and re-save the new cut file. Make sure you are using the VCarve toolpath and that you are starting the cut at 0.00. If you start deeper the stars will be larger and have round corners.
It might also be the bit. The way most v-bits are made the point is not really pointed but actually has a flat tip. Some of them have a pretty good size flat tip. For perfectly sharp corners on things like stars, a three flute bit like this is needed.
It might also be the bit. The way most v-bits are made the point is not really pointed but actually has a flat tip. Some of them have a pretty good size flat tip. For perfectly sharp corners on things like stars, a three flute bit like this is needed.

60-Degree V-Groove Bit, 1/4-Inch Shank, 1/2-Inch Diameter, Carbide-Tipped - Straight Router Bits - Amazon.com
60-Degree V-Groove Bit, 1/4-Inch Shank, 1/2-Inch Diameter, Carbide-Tipped - Straight Router Bits - Amazon.com
www.amazon.com