Generally speaking Don to service the trans or change the fluid, a filter/ o-ring & gasket is part of normal servicing & with the kit.
So chances are if you had the fluid serviced professionally, the filter was probably replaced.
I experienced hard shifts when it got hot after hwy runs mainly and my 4t65e and would almost bang in between 2-3 gear. In the accumulator (found once you drop the pan) there are two barrels a 1-2 & 2-3 and they often can accumulate some varnish & get a bit sticky too. (same with pressure solenoids in valve body) I used 1000 grit emery cloth to smoothen out the barrels, and installed the trans go spacer & spring shift kit, which I did myself and was not that hard. It comes with good instructions. Dexron VI (6) was added and has not banged since.
When u say no codes, was it read by a professional or good code reader than can read body/trans codes? You wont get a Engine light normally.
What I would try is this. Get a can of Seafoam Trans tune: Trans Tune - Sea Foam Sales Company
Add the whole can if u got room,and see if the shifting conditions improve on highway etc. This will remove varnish from trans areas that need it including accumulator valves/barrels.
It generally takes about 500 miles of hwy driving for it to work best.
If conditions improve even slightly ..I would then consider your trans still a candidate for now a Trans go kit, and new filter/ Dex 6.
If there were ever lots of fine or chucks of particles found in the bottom of pan or on magnet, I would pass & rebuild the trans completely.
Also check your forward engine mount closest to the rad for any cracks.
I want to add for the trans to shift properly as well the engine should have a good state of tune.
Had a friend call once complaining of trans problems only to discover the engine needed plugs/wires/fuel filter Iac cleaning/throttle body cleaned, to get it to run right & shift again properly.