Unable to handle conflict reported by NSCloudKitMirroringDelegate

I'm working on an app that uses NSPersistentCloudKitContainer to handle CloudKit sharing. Against all odds I've gotten the sharing to work, but now I'm seeing errors on startup that look very much like some kind of background loop trying to merge changes from multiple users and failing.

In a more traditional CloudKit installation not backed on NSPersistentCloudKitContainer this feels like a case where I'd have to provide some code to handle the merge.

In the brave new world I can't seem to find anyway to affect this Mirroring Delegate. It starts when I initialize the NSPersistentCloudKitContainer and produces the error below (as well as a long stream of similar errors).

Any ideas?

error: CoreData+CloudKit: -[NSCloudKitMirroringDelegate _exportFinishedWithResult:exporter:](1347): <PFCloudKitExporter: 0x282d2ead0>: Export failed with error:

<CKError 0x280079470: "Partial Failure" (2/1011); "Failed to modify some records"; partial errors: {

	cloudkit.zoneshare:(Pacts:__defaultOwner__) = <CKError 0x280079680: "Server Record Changed" (14/1022); "Participants conflict while trying to update share from the server. Participants:

=== Client: (

    "<CKShareParticipant: 0x100cebb70; participantID=..., isCurrentUser=true, role=owner, permission=readWrite, acceptanceStatus=Accepted, identity=<CKUserIdentity: 0x100c4cae0; userID=__defaultOwner__:(_defaultZone:__defaultOwner__), nameComponents=, cached=false, publicKeyVersion=2>, hasProtectionInfo=true, invitationTokenStatus=Healthy, isAnonymousInvitedParticipant=false>"

)

=== Server: (

    "<CKShareParticipant: 0x100c26db0; participantID=..., isCurrentUser=true, role=owner, permission=readWrite, acceptanceStatus=Accepted, identity=<CKUserIdentity: 0x100c13b60; userID=__defaultOwner__:(_defaultZone:__defaultOwner__), nameComponents=..., lookupInfo=<CKUserIdentityLookupInfo: 0x100c13c00; email=...>, cached=false, publicKeyVersion=2>, hasProtectionInfo=true, invitationTokenStatus=Healthy, isAnonymousInvitedParticipant=false>",

    "<CKShareParticipant: 0x100c25960; participantID=..., isCurrentUser=false, role=user, permission=readWrite, acceptanceStatus=Accepted, identity=<CKUserIdentity: 0x100c259f0; userID=_6cd4c7c8091c946d4b8e704efbfc0bc4:(_defaultZone:__defaultOwner__), nameComponents=..., lookupInfo=<CKUserIdentityLookupInfo: 0x100c68d10; email=...>, cached=false, publicKeyVersion=2>, hasProtectionInfo=true, invitationTokenStatus=Healthy, isAnonymousInvitedParticipant=false>"

)">

}>