Assuming all other settings remained the same:
3 minutes is about 1/2 stop more than 2 minutes. I wouldn't expect to see much difference. It doesn't matter that you're dealing with long exposures, the same basic photography rules apply. Try exposing for 5 minutes and see what happens.
You need to be more specific. What camera(s) are you using and what settings are you using. How are you metering?
We are not sitting there with you looking at what you are doing.
Did you ever find a solution? I have the root certificate working on the A7CII and used to have it working on the A1, but after the 3.00 firmware update, it no longer works.