Sir, I would really recommend going to a transmission/oil change specific shop, as opposed to the dealer. First thing I would recommend is a reverse flush and refill of both your coolant, and transmission. I would also recommend a complete flush of your brake system.Edit; I think I had it updated in 2016 or 2017? Is there anything newer that will help. Cheers.
When you did your drain/refill, did you change the filter? I would see how much the shift solenoids are, and whether or not you could access them by dropping the pan.I have pretty much done everything in list, just not a flush. Not sure a transmission flush is safe at almost 300,000 km? Could it cause more problems? I have done some drain and refills.