Are you using entirely NSI products?
Like Nail Pure, Cleanse, Vanish etc etc or are you mixing products?
What lamps are you using?
You must use a 36w (4 bulb) lamp.
You say you are doing prep correctly, can you take me through your steps?
I have used PP since it was first launched here in Australia and continue to use it to this day (so about 2 years) and apart from the first formula being a bit too thick, I have never had any problems.
Once NSI changed the formula and offered the new "Renew" thinning product, I have not had any problems at all and absolutely love it.
To be honest, I have only had to use the Renew 2 times since I bought some and I have nearly every color of the entire range and use them all.
There are a few key elements:
Thin layers and only capping the base and top coats not color coats.
Not touching any skin is paramount.
Making sure your prep is done correctly.
The correct lamp.
Correct after care.
If you want to tell me what your steps are, I will try to help further