Do you know what your shift point is vs the rev limiter? And also what type of power do you have? Let’s say you have a rev limiter of 7000 and want the shift roughly at 6800 so for the 2-3 shift you need to “lead” your shifts, my trans builder told me think of it this way, the electronic part you are playing with is instant but the hydraulic aspect isn’t, so it needs time, if you want a shift at 6800like in my example on a roughly 450-500 hp car the shift rpm should be set to 6400 and see where it actually goes to and adjust accordingly, I was having the same issue and bought a built trans thinking it was the trans, turns out it was the tune, but anyways a good way to try it would be to zero out the mph for up shifting in the WOT shift table and so it looks for only an RPM, and if you want the shift at let’s say 5800 from what it showed me try setting it to 5400 and try it, if it’s early then up to 5500 and so on till you are happy with the point it actually hits the shift at, and shifts feel “mushy” or sloppy per say you can play with pressure to help it

while you and the computer may be trying to command 3rd at lets say 5800 the trans has to turn off the band for second and activate the clutches/solenoid for 3rd simultaneously so it likes being told sooner and then it will end up where you want it if that makes sense.