Thanks for the response, Gabriel. I've made sure to follow your instructions exactly for troubleshooting purposes - still getting the same issue. The specifics:
I have 29 lines on the medical expenses form on the Interview tab.
These 29 lines total to $3873.25. I've added them up in MS Excel and two calculators. I've also copied them line by line from the form and totalled them.
The amount on the Results tab is $3718.25, which is a difference of $155.00.
$155.00 is the amount of the first line on the list.
An interesting data point is that it doesn't matter what I change that first line to - I can change it to whatever random number I choose ($255.00, $1444.25, or $1.30) - the Results total is still $3718.25. This tells me that the first line isn't being included in the total for some reason.
I'll go ahead and email the support team at the address you provided. I appreciate the help.