Short Shifter keeps poping loose on my Boxster

[gd2aan]

I have a 2000 Porsche Boxster that I had my Mechanic install a B&M short shifter and it keeps poping out leaving my car in first gear. This has now happened 2 times and the mechanic now says the the transmission needs a fluid change. That is why this happens.

I find this hard to swallow since everytime it popped out I was turning at a stop light at low speeds and it popped loose. The sifter when first installed was nice and tight then started to get a little further between shifts then popped out. The 2nd time I picked up the car and noticed that it seemed a little far between shifts but chalked it up for non use for about 3 weeks and was wrong. Now it seems to be related

They charged me 1300.00 to do the install and for the shifter.