UI spins indefinitely after bulk send. Network shows POST /api/rest/v6/megaSigns → 429 THROTTLINGTOOMANY_REQUESTS with body { "retryAfter": 76918, "message": "…try again in 22 hours." }. Region na4. Please surface this message to users and disable the send button until the window resets. (Include timestamp, account email, and the Request/Trace-ID from response headers if present.)