Cracking Multiple Coolant Reservoirs

Bought the car in November and in early December I found a puddle of coolant under my car. Found a crack in the reservoir. I learned through research that this is a fairly common occurrence in these cars.

Bought a new reservoir from JHM. Installed it and had no issues. Today, 4 months later, I found a new crack in the reservoir. It’s at the top of the reservoir so it’s actually not leaking coolant this time, however, it can’t build pressure, lowering the boiling point of the coolant.

I’m going to buy a new reservoir but my question is what would cause reoccurring cracking of the reservoir. I know it’s a common occurrence but 4 months?

Thanks ahead of time.