1999 Suburban 1st to 2nd shift sometimes hard shift under light loads

I bought this suburban and love it. 124k Miles. The engine is great and smooth running and the trans shifts great in normal load conditions but I live in Atlanta and get stuck in traffic to and from work and when
this happens under light load the shift from 1st to 2nd seems a bit hard sometimes and I feel fair jolt/quick push forward. All other gears are fine! I'm wondering if its just the trans getting old or if it is something else.
History
Purchased it from the original owner. It was his wife's suburban and I know this lady and she baby's her vehicles. This fluid was changed once at 40K miles and I just changed it with fluid/filter and a new filter gasket. The gasket was a trick to be pressed in but I'm a fair mechanic and was able to replace it with a good fit flush to trans housing. The filter went in good and its good and tight fit in the gasket. I cleaned the pan well and reinstalled the original magnet after cleaning. The magnet was covered with very fine paste but this build up was normal for a vehicle with this millage. No leaks before or after.
Thanks in advance!!
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My '99 Yukon's trans has an adaptive mode. (Factory tow package) When trans goes through a few heavy throttle shifts it automatically goes into a tow mode that firms up the shifts. Stays in that mode until ignition is cycled off. When I first got the truck I thought the trannie was taking a dump but a little reading filled me in on it. Newer trucks now have the tow / haul button on the dash to eliminate the annoying adaptive mode.

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