Identify what is being displayed

1. Read the object's reliability/status and compare with the Modbus source diagnostics. A visible value can be the last successful reading after a source failure.
2. Check whether the COV subscription was accepted and is still active. If denied or expired, use the client's supported resubscription/polling arrangement. Check thresholds before assuming that no change notification means failure.
3. Compare source update rate, configured polling, and available freshness information. Firmware exposing proprietary property 1306 reports time since the last successful poll.
4. For a writable object, inspect the active write priority and whether the client has relinquished its command.
5. Check SB1000's writable-point mode. Hold keeps Present_Value under the priority array until relinquished. Follow the bus writes a command once, then reports the field device's value.
6. Read actual equipment feedback. A retained command, a Modbus setpoint, and physical feedback can be different points.

Expected result

The displayed value and quality reflect the intended command/readback behavior and acceptable age. Restore or release test commands afterward. Include object identity, priority/mode, source status, and timestamped values if the difference is unexplained.