Having dropped 2 k-members (Front Suspension Crossmember Sub-assembly
) and confirmation from a 3rd individual, there seems to be an unknown corrosion issue on the passenger side of the K-member mounting points. At the time of this posting, it is unknown if Toyota knows anything about this. If more people discover this issue with their tC's, go to the Dealership immediately and have it addressed. Corrosion is no small matter when it comes to bolts, especially suspension and steering ones.
I will add a poll and leave this topic open for discussion.

This diagram shows the location on the passenger side frame mounting stud/nut (marked in red) that has corroded threads. The driver side stud/nut has only normal corrosion.

This is the actual corrosion on the cross-member, lower side where the nut attached to the stud.

This is the actual corrosion on the cross-member, upper side where the stud runs through.

This is the actual corrosion on the rack-and-pinion mounts for the cross-member.

This is the culprit, the A/C condensation drain. It drains directly onto the cross-member, puddling ontop and inside.

A simple fix is to attach a 3/8 ~ 1/2" ID vacuum line to the same size 90° elbow; ziptie together.

Here is the completed mod. Easily done with the aid of ramps or a jack with safety jack stands. It directs the condensation droplets harmlessly down and rearward into the airflow under the car. It can be position to drop onto the s-pipe where it will dissipate quickly as steam.