2001 S transmission slip from 2nd-3rd
 

Greetings All,
Most recently noticed the transmission seeming to slip between 2nd and 3rd.
Specifically, when accelerating hard through an intersection and making a turn, the car’s rpms spike and the transmission doesn’t shift to third until I have taken the foot off the accelerator.
Should mention that it is an automatic/Tiptronic transmission.
The problem does not occur when driving in manual/Tiptronic.
Has anyone experienced / heard of this before?
Would appreciate some feedback.
Thanks
Markus