@Corsac thank you for your quick response!
I have (or at least as of last week had!) the most updated versions of both D.T and the plugin.
From the error log, it looks like the issue is that it wants me to update (or fill in) most/all unanswered fields.
I don't want my users to have to fill in every field (but I would like them to fill out the fields for which they have information)...
The error log is showing this message:
update_post
status: 400
key_select value must in string format: faith_status
{When I fill in the specified field, it continues to be unable to update the contact and the error log shows that the next blank field needs to be filled in.}