Do I think you have a problem...no but join the slightly miffled/baffled mx30 club. This forum is full of chats about charging times, cold weather effects on ev batteries etc. The mazda claim of 20 - 80 % fast charge in 40 minutes is based on that charge range and the test area conditions. Evidence shows a slow down of fast charge rate beyond about 55% and also when batteries get colder. So at what % did you start the fast charge? Also public chargers can vary in effectiveness and not deliver the advertised rate of charge. It sounds like you public charger was perhaps only delivering 3.6kwh?
Type slow charge into this forums search community above and have a look. Lots of clever mx30 owners feedback and rational re charging.
As discussed on this forum we reckon the mx30 has only got about 30.5kwh battery available within the 0 - 100% range and the rest of the advertised 34.5kwn is the upper and lower buffer. The ac charger control in the car limits you to 6.6kwh max. So on ac you cannot charge above that rate. So do the sums re ac charging timescales. Then the other factors come into play. DC charging (50kw) is another game re state of charge v timescales v control v conditions that are beyond me. See the links below:
Fastned recently had the opportunity to test fast charging performances of the all-new Mazda MX-30, which was supposed to recharge from 0-80% in 40 minutes.
The complete guide to charging your Mazda MX-30 (2021), covering electric range, how long it takes to charge, how much it costs, and much more.