Most likely you are shooting to hot. Take your plastic to 350F to fully change state (and stir so all of it is the same temp!) and let it cool to 330 and see if the dent goes away. If not, try 220.
The problem is that the skin of the bait cools first and the hot center contracts as it cools causing the bait to "suck in" somewhere (called differential cooling). The hotter the core is, the worse the dent is.
When you reheat, only reheat to the best temp for that mold. I shoot a lot of molds at 320F, as long as the flow is good enough to fill legs, tails, etc.
