I was recently involved in a consulting project with a common issue…
The company has purchased a new mold and trials were run. Unfortunately, the PP parts were failing performance tests and exhibiting cracking. The company was investigating the tool in hopes of determining what is different with the new tool.
Upon investigation, the tool was not much different, but they were not using a process similar to that of the production tool. They were using less than 5% of the overall cooling time to recover the next shot causing the material to become over-stressed during melting. Additionally, they were using time for 1st stage transfer causing over-packing during 1st stage fill. This creates additional molded-in stresses in the part contributing to the part failure.
Just because you are running trials does not mean you can rush and cut corners. Always take the time to develop a good process so you can derive applicable data form your efforts.