Master bedroom won’t cool down

We have a new build that is roughly 3000 square feet, single story, built in 2021.
The builder installed a single 3.5 ton unit.

We live in a hot and dry climate, where the summers can get into the highs of 110s for several consecutive days.
The first year we lived in the house, we had no issues with any of the rooms cooling down. By the 2nd summer, there was a refrigerant leak, but it was fixed by the builder.

Since then, we have had ongoing issues with our master bedroom, which has multiple windows, is in southwest corner of the home and has 2 vents to that room.

This a/c cannot keep up with cooling this room down in the summer and it can’t get below 76 degrees overnight.
We put up window coverings and tint and bought a 1 ton window unit which all helps, but once the window unit is shut off, the room heats back up.

The rest of the house is fine.

We have had multiple hvac companies come out and say everything is working; airflow fine, temp of the air blowing out is fine and suggest getting a larger unit or a mini split. But we feel there has to be something wrong because there was no issue in the first year prior to the refrigerant leak + all other homes with the same model do not have this issue.

We are at our wits end with this.
Does anyone have any ideas ? What questions should we be asking these hvac technicians to check? Is it a ductwork problem?