"If you are concerned about the status of your seat belt prior to your scheduled inspection, you may be able to detect this condition by pulling very firmly on the lap portion of your seat belt with a force of at least 80 pounds. This procedure may detect an improperly attached seat belt but performing this procedure does not replace the need for an inspection by a Tesla technician."
It's cool that they're being so straightforward, but it's weird to see that sort of procedure so casually recommended to the end user.
Edit: I got my appointment scheduled for next week. Pretty quick and easy. I was afraid it might be a substantial wait, as the last time I needed a service appointment they were booked for a month. This inspection is only supposed to take 20 minutes, so maybe they're able to squeeze it in earlier because of that.