noisy roof

Hi!! So happy to find this forum- we purchased a mid century modern home in central Austin- been here a month and mid day in the heat this roof pops like crazy!! Sounds like someone is pitching various sized balls at the roof.
I had a roofing person who does install metal roofs come and check things out- the middle of the home has attic space so it is quiet there and has open cell insulation. On the ends of the home the roof is right over the ceiling where it is most audible.
There is no ventilation/baffles or air intakes. We are not sure if there is or what type of insulation in the ends of the home. The current roof is a 26 g flat metal, and I guess lots of waves from the heat.
I will be attaching photos of the home to give you an idea of how it looks, I am also going to ask the previous owner about warranty.
I tried to look at city permitting to find the insulation but no dice.
So my query is would you recommend changing the roof to add in air ventilation? Do you suggest 24 g metal? They have a 24 g that is not flat so it allows for movement.
Thanks so muchEES15.0019 7809 Tisdale permit set 4-19-16 (dragged).pdf_e9b9942a9450130c0f429b55dd597688.pdf)