04 GTP Comp G Shifting Hard from 1st to second gear

My friend has an 04 grand prix gtp thats shifting hard from first to second gear, seems like its slipping sometime and dosent want to shift. He has flushed and replaced the trans fluid and filter with no change in issues.

Vehicle background: All stock, 109,906 milage


Will post scan logs and tune soon

Sometimes a hard shift is result of excessive slippage and the accumulator maxes out and then all the sudden it is full on pressure to apply the clutch. 2nd is known for this as it has very loose factory clearance and there is a long delay for the shift to complete. Add in high mileage and overall wear and the problem gets worse. The best and really only way to see what is really happening is to have the car diagnosed with a scan tool and watch the 1-2 shift time and commanded pressure. There are other reasons to have a harsh 1-2 shift but this is one that is more common to see. Broken accumulator springs, stuck valves in valve body, etc can also cause harsh shifts.