Strange thing happens when I bias my amp

I tried to bias (at 100 mA) my newly acquired used Cary SLI-80 integrated using a standard multimeter set to DC current. WIth no input signal the bias current was over 200 mA initially, then decreased (seemingly) exponentially to 0 with a time constant of 1 to 2 minutes. This happened in both channels. The amp works well and sounds great to me by the way. I am curious as to what's going on and would like to know if there is a problem I need to address. Any advice from members with expertise in electronics is appreciated. Thanks in advance. Dave
For ss amps, TNT Audio has a great article explaining how to set the bias of your amp. Google 'adjusting the bias of your amp'. But it doesn't talk about mosfets, only bi-polars. Mosfets are adjusted by removing a rail fuse and putting an ammeter (setting your multimeter to mA) across the contacts. One channel at a time. The fuse contacts, that is. Not the mosfets. Ideally both channels at the same time with separate multi-meters.
Basic guesses are usually the best guesses and that is:

your multimeter settings are wrong

you are grounding improperly

some connection sequence is incorrect

Regardless, contact Cary for further instructions.