A brief black screen can result from a signal interruption even when the monitor remains powered. High resolution, high refresh rate, HDR and other signal settings can place different demands on a connection. Temporarily reducing that demand is a diagnostic experiment: it helps isolate the route but does not establish which component is defective on its own.
Capture the conditions before reducing demand
Record whether one display or both goes dark, whether audio or USB devices disconnect, and whether the monitor reports a lost input. Note the active resolution, refresh rate, HDR setting, dock model and cable path. A blackout that coincides with an entire dock reconnecting suggests a different investigation from a single screen briefly losing video.
Choose one supported lower refresh rate or resolution in the operating system's display settings. Keep the other variables steady, including the application and physical cable arrangement. Run the workload that usually triggers the fault for a meaningful observation period. A few quiet seconds are weak evidence if the original interruption normally occurs only after extended use.
If the interruption stops, restore the previous setting to see whether the behavior returns. Avoid repeatedly pushing a visibly unstable setup when it risks interrupting unsaved work. A consistent relationship between a particular mode and the fault is useful evidence, but it can reflect cable quality, adapter capability, a shared bandwidth limit, firmware or the source output.
Narrow the route without changing everything
Consult the documented mode limits for the exact host, dock, adapters and monitor inputs. A connection that works for one display alone may not support the same mode with two displays active. Product labels such as USB-C or HDMI do not, by themselves, specify the complete capabilities of a particular port and route.
Where the hardware supports it, test a direct connection that bypasses one intermediate device. Preserve the same display mode when comparing routes, or explicitly record the difference. If the direct route is stable, that narrows the investigation to what changed; it does not automatically prove that the dock alone is faulty rather than its cable, power or configuration.
Try a suitable known-good cable without bending connectors or moving the whole workstation at the same time. Check whether the interruption follows the cable, the monitor, a port or a specific application. Keep any firmware or driver update as a separate controlled step, following the relevant manufacturer's instructions and retaining a recoverable configuration.
Use the stable supported mode while collecting evidence for further support. Report the exact failing and passing combinations, including whether the second screen was active. That record is more actionable than a general claim that the monitor sometimes flickers. The goal is to identify a reliable configuration and explain its limits, rather than disguise an intermittent failure with an undocumented setting change.