The rubber sleeve of the adapter plug prevents it from going fully into the Leappad or Leapster 2 unit,resulting in not a very tight fit, thus the power loss when moved.
I found that to get this adapter to fit firmly into my GrandDaughters LeapPad, I had to cut approx 2mm off the end of the rubber sleeve, which made it fit further into the Leappad Power socket, giving a better fit.
I also used a little Electical Tape to keep the main Pin and Adapter together (to prevent my little darling from pulling it off!)
This resulted in no Power Failures whilst playing with the LeapPad (I mucked about with it for about 30 mins or so). The plug stayed in without any problems.
I hope this may be of some assistance.