A gurgle heard at the sink describes the shared drainage arrangement as well as the appliance. It does not automatically mean the washing-machine pump has failed.
Understanding this situation
Note whether the sink also drains slowly during ordinary use, whether water rises and whether the event began after plumbing work. These observations can help distinguish an appliance issue from a concern in the connected waste route.
A useful next step
Do not disconnect hoses or use aggressive drain chemicals through the washing machine. Stop use if water backs up or escapes. Describe both sink and washer behaviour to the booking team so the appropriate scope of work can be considered.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.