Variance in Electrical Leakage for High Voltage Dielectric Testing

Hi, I have encountered problems while testing safety boots in a high voltage dielectric tester. Each time when I test 6 to 8 boots the leakage current is relatively high compared to testing the same boots but with lesser amount, lets say 1 to 2 boots. This variance in reading causing the boots to fail when tested in one go. So if someone could suggest how to overcome it or what are the factors that causing the difference in reading would be really helpful.

YOur test method is not described not expected BDV voltage and current displayed. Is it from moisture creepage or contamination or proximity of all the boots near the one under test? SHow a diagram and your test method. Also, can you listen to a quiet channel on AM while testing for ticking sounds and note the threshold voltage of any events

The test is actually a wet test method with boundary voltage of 5kV and the limit for leakage current is 5mA. Sorry cause there is no available pictures for the tester but I have attached a youtube link where the tester used is almost similar to mine. And I actually don't get it, what is AM and how does ticking sounds can effect the leakage current.
Link: Thank you, for the suggestion and feedback it was very helpful.