CRM - Internal Server Error: when working on multiple entities - dynamics-crm

Question

So I have a custom action (an approval button) that can be triggered either when editing a single entity or for multiple entities when triggered from the entity list view.
The logic essentially removes one entity type and creates a different one with more fields and options available after approval.
The logic works just fine when it is triggered from the Form where there is just a single entity being edited.
However when the same logic is run from the list view and now I am iterating over multiple entities, there is in internal server error when I try to create the record for the new entity type (the one with more options). This makes no sense, I am calling out to a function which already works under a different scenario. And I am creating a new entity, not updating or deleting an existing one so there should be not locks or other concurrency issues.
The the error is gloriously uninformative and I can't see any logs anywhere that would help me debug this. Has anyone run into this before?
Edit
I have enabled CRM Trace Logging for errors (in the registry), however this does not help. This internal server 'Error' does not seem to be errory enough to show up in the logs.
Edit 2
Perhaps some code? The error happens on the SDK.REST.createRecord line, but only when it is run inside the loop of the click handler, when it is run from single entity form, it creates a record without issue.
PCL.EventParticipants = {
EventFormApproveParticipantClick: function (selectedItemIds, entityTypeName) {
debugger;
var anEventRequest,
requestId,
action,
event,
contact,
emailPref,
actualEmail;
console.log('Approval Clicked');
// Do this if we are working on a single event request
if (entityTypeName == null)
{
requestId = Xrm.Page.data.entity.getId();
action = Xrm.Page.data.entity.attributes.get("pcl_action").getValue();
var participant = PCL.EventParticipants.MakeParticipant(
Xrm.Page.data.entity.attributes.get("pcl_contact").getValue()[0].id,
Xrm.Page.data.entity.attributes.get("pcl_event").getValue()[0].id,
Xrm.Page.data.entity.attributes.get("pcl_name").getValue(),
Xrm.Page.data.entity.attributes.get("pcl_emailpreference").getValue(),
Xrm.Page.data.entity.attributes.get("pcl_selectedemail").getValue()
);
if (PCL.EventParticipants.Act(requestId, action, participant)) {
alert('Approval complete.');
}
return;
}
var opSuccess = true;
// When multiple requests are selected do...
for (var x = 0; x < selectedItemIds.length; x++) {
requestId = selectedItemIds[x];
SDK.REST.retrieveRecord(
requestId,
"pcl_eventrequest",
"pcl_eventrequestId,pcl_Action,pcl_Contact,pcl_Event,pcl_name,pcl_EmailPreference,pcl_SelectedEmail", null,
function (anEventRequest) {
requestId = anEventRequest.pcl_eventrequestId;
action = anEventRequest.pcl_Action.Value;
var participant = PCL.EventParticipants.MakeParticipant(
anEventRequest.pcl_Contact.Id,
anEventRequest.pcl_Event.Id,
anEventRequest.pcl_name,
anEventRequest.pcl_EmailPreference,
anEventRequest.pcl_SelectedEmail
);
if (!PCL.EventParticipants.Act(requestId, action, participant)) {
opSuccess = false;
}
},
function(error) {
alert('Could not retrieve selected event request: ' + requestId + ' Check that it has not been removed from the system. --> ' + error.message);
}, false
);
}
if (opSuccess) {
alert('Approvals completed.');
} else {
alert('One or more Approvals failed.');
}
},
Act: function (requestId, actionValue, participant) {
var opSuccess = false;
if (actionValue == '798330000') {
// Add action
opSuccess = PCL.EventParticipants.CreateEventParticipant(participant);
}
if (actionValue == '798330001') {
// Remove action
opSuccess = PCL.EventParticipants.RemoveEventParticipant(participant);
}
if (opSuccess == false) {
return opSuccess;
}
opSuccess = PCL.EventParticipants.RemoveParticipantRequest(requestId);
return opSuccess
},
CreateEventParticipant: function (eventParticipant) {
var existingParticipant = PCL.EventParticipants.RetrieveEventParticipantLike(eventParticipant.pcl_Event.Id, eventParticipant.pcl_Contact.Id);
if (existingParticipant != null) {
alert('Cannot approve this request. This contact is already participating in the selected event.');
return false;
}
var opSuccess = false;
SDK.REST.createRecord(
eventParticipant,
"pcl_eventparticipant",
function (result) {
opSuccess = true;
},
function(error) {
alert('Could not create event request with contactId: ' + eventParticipant.pcl_Contact.Id + ' and eventId: ' + eventParticipant.pcl_Event.Id + '. --> ' + error.message);
}, false
);
return opSuccess;
}, .....
}
Edit 3
I have modified the SDK.REST to have a 5th parameter which toggles whether or not the operation is synchronous or asynchronous. Passing false at the end of any operation makes the operation synchronous.