A conversation participant who was sent as one of your senders now has the same label everywhere, including in old conversations.
What you need to do. Wherever you check who a participant is, match "sender" instead of "sender_identity":
if (participant.actorType === "sender") {
// sent as one of your organization's senders
}
The old value is gone from the SDK's types, so code that still uses it stops compiling. That makes the change easy to find: your build will point at each place.