Inspect received ACK route before clearing its header

src/helpers/BaseChatMesh.cpp

@@ -495,12 +495,13 @@ void BaseChatMesh::onAckRecv(mesh::Packet* packet, uint32_t ack_crc) {
   ContactInfo* from;
   if (processAck((uint8_t *)&ack_crc, from)) {
     txt_send_timeout = 0;   // matched one we're waiting for, cancel timeout timer
-    packet->markDoNotRetransmit();   // ACK was for this node, so don't retransmit
 
     if (from != NULL && packet->isRouteFlood() && from->out_path_len != OUT_PATH_UNKNOWN) {
       // we have direct path, but other node is still sending flood, so maybe they didn't receive reciprocal path properly(?)
       handleReturnPathRetry(*from, packet->path, packet->path_len);
     }
+    // Check the received route before marking, which replaces the header.
+    packet->markDoNotRetransmit();   // ACK was for this node, so don't retransmit
   }
 }