First, before saying something is a "problem", it would have been best if you checked the release notes, since this is obviously intentional, and lots of users asked for it, since they complained the previous solution of always having the same number of carts no matter the load was unrealistic.
Our previous reasoning for having the number of carts fixed, was because originally (we always had variable carts in years), we had the support swamped by questions from users who failed to understand how payload and/or number of passengers affected the calculation of carts and, since it took quite a bit of amount of costly support time having to explain this over and over, because nobody ever reads the manual, we made GSX "dumber" in MSFS, with a fixed number of carts, and this reduced the support effort, because all those questions "why I have only 1 cart" (or any number lower than expected) stopped.
But we listened to users, and we were convinced that no, users are smart, and it's wrong to make GSX less realistic, just because people don't read the manual, so we put the variable cart feature back on, as it was with FSX/P3D for years, but I was sure those questions would reappear.
So, I'm NOT going to explain it fully here, because there's a page in the manual completely dedicated to this question, at Page 81, the chapter named Variable number of Luggage/Cargo carts., which explains in full detail how the number of cart is affected by Passenger Number, Payload or Simbrief (if you use it) and how it changes if you don't use it, and if the airplane is Cargo or not.
So, first read the manual, and only report this as a "problem", if you think GSX is not behaving according to the documentation, providing then a full diagnostic log for that flight, which would record all the variables involved in the calculation, which we can use to check if yes, we have a problem or not, you just don't understand how the variable number of carts is calculated now.
