16 cavity stick molds, I routinely shoot with the temp controllers hovering around 170C (338F) with the actual plastic around 330. Never have I had a denting problem, maybe, and this is a huge maybe, I get 5-10 out of 1000 stick baits with a dent. Further, ZERO colour issues, including white. Only fading I've ever seen is with specific dyes, all other dyes and pigments I have no issues with. It seems that as soon as I went with my own mold (I specified the layout, runner and gate design as well as the cavity design) I had no issues with dents.
For the OP. The reason they dent as Frank noted is the gate is too small for the bait. Plastic expands as it is heated and then contracts as it cools. To prevent the baits from getting dents as they cool you need a fresh supply of hot plastic to feed the cavity as it cools. If the gate isn't large enough it will freeze off before the bait is cool enough and the only thing it can do is shrink and pull from the side causing the dents. One fix is to shoot your plastic cooler as it will actually contract less. Another is to hold pressure after filling the cavity. If the gates are that magic size they will sufficiently feed the cavity as it cools. Also remember, you still need to bring your plastic up to proper temperature of 350 when you initially cook it, then back the temperature off to your shooting temp.