I am getting inexplicable Maps.Events directionsErrors: We can't find directions between one or more waypoints.

I am using Bing Maps REST API via java script. My routing application is working well for virtually all customers in all scenarios. I have one customer getting errors like this in only some scenarios:

We can't find directions between one or more waypoints. Check your waypoints and route options and try again.

I have a copy of their locations and can replicate the issue at will. I will describe the scenario in general concepts to show what is confusing.

I map a set of 20 locations and it works well. Starting with those 20 locations in each point below:

• Remove one of a certain subset of the locations - no error.
• Remove one of the disjoint subset of the locations - error.
• Remove any two or more of any of the locations - no error.
• Add one or more new locations to the set of 20 - no error.

The non-error subset and the error subset are constant and predictable. The removal of a single, given location always produces the same behavior. Randomly reordering the locations before mapping makes no difference in any of these scenarios.

Update Mar 14, 2024: Adding a code snippet, a sample data point, and a screenshot.

//Sample data point element:
{lat:26.098341500000000,lon:-80.365857200000000,nm:'FALK \u0026 FALK, P.A.',ad:'1655 N Commerce Pkwy',ct:'Weston',st:'FL',zp:'33326-3276',co:'US'}

//Code snippet:
function addWaypointsDM() {
    try {
        var idx, loc, waypoint;
        for (idx = 0; idx < gcodes.length; idx++) {
            loc = new Microsoft.Maps.Location(gcodes[idx].lat, gcodes[idx].lon);
            if (gcodes[idx].ad.length > 0) {
                waypoint = new Microsoft.Maps.Directions.Waypoint({ location: loc, 
                    address: gcodes[idx].nm + ' - ' + gcodes[idx].ad
                });
            } else {
                waypoint = new Microsoft.Maps.Directions.Waypoint({ location: loc,
                    address: gcodes[idx].nm + ' - ' + loc.toString()
                });
            }
            directionsManager.addWaypoint(waypoint);
        }
    }
    catch (err) {
        showError('showStops:addWaypointsDM', err.message);
    }
}