Why does my suv jerk while hitting 25-30mph (always) rmp jumps to 4!

I have a 2016 Ford Explorer XLT- I noticed my SUV jerking when it hits in between 25mph-30mph. once i hit that limit my rpm Gage jumps automatically to 4. I do not like it at all. I have already took it in where I purchased my vehicle and at that time they only noticed a shift solenoid being out. Once I got it back that when I noticed my vehicle jerking (always at that speed 30mph) and the rpm Gage jumps up to 4 This is my first time buying an expensive vehicle and i am not impressed! Any answers what might be wrong with it?