Car jerks when 1st gear shifts. Help?

I have a 2003 honda accord coupe v6 automatic with 198000. So every time the gear shifts from first gear to second gear, the car jerks. However, if i do not press on gas pedal while the gear shifts, it changes smoothly. This only happens on first gear to second gear, the rest of gear shift smoothly. What is going on? Is the transmission about to give?
I read online to do a transmission flush and that make fix the problem. What do you guys think?

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