Sim Tray material short circuits?

I had this conductive sim tray problem with my iPhone4.

Solution is to use a thin coating of nail polish between the overlapping areas between the sim and the tray.

The nail polish, (clear coat/nail hardener -best option) works as an insulato, blocking conduction between the sim and the carrier.

Avoid lathering the nail polish, only a very thin painted coat is necessary. Make sure any excess nail polish is scraped gently away from the sim or sim carier. Too much polish will prevent insertion of the sim carrier back into phone, any excess left can flake off and float around the inside off the phone and may cause problems.

Do not cover the portion of the sim card that needs to connect with the contacts inside the phone.

Likewise if you have one of the early iPhone4 that had the attenna problem, you can paint the aluminium edge with polish thus preventing your fingers shorting out the attenna/reducing signal. This means you can use your early iPhone4 without a bumber case. Later iPhone don't have this problem.