What affects the chance to get ambushed on Framing Frame Day 2?

Solution 1:

I've seen and heard a lot about this ambush.

From my experience, finishing the day one without triggering the alarm will insure you to avoid it. The wiki seems to confirm it:

Note: If you have successfully completed Day 1 in stealth, you will not be ambushed on Day 2.

It also says that

If you have not successfully completed Day 1 in stealth, there is a chance you will be ambushed though it is random, it is possible to go loud on Day 1 and have no ambush on Day 2 if you escape during the hostage phase.

I've also seen a guy putting an ECM jammer on the cell phone instead of answering it, before the second phone call. He wasn't sure, but thought it would reduce the chances of an ambush.