An offset that grows during playback suggests a timing or clock-handling issue rather than a simple fixed lip-sync setting. The source, player, decoder and audio route can contribute. Note whether seeking or reopening playback temporarily restores sync, because that helps distinguish drift from a constant delay.
Measure the pattern
Watch a clear speaking scene near the beginning and again later. Record roughly how long it takes for the mismatch to become noticeable. If pausing or seeking resets the relationship, include that observation. Do not keep increasing a delay slider every few minutes; that treats the symptom while hiding useful evidence.
Compare a stable reference
Try another authorised programme with a different format in the same player, then the original source in another supported player if practical. Keep the same speaker route. This can help separate a source-specific timing problem from a device-wide issue, without assuming that every sound fault comes from broadband speed.
Report a reproducible sequence
Provide the device, app version, audio output, selected track and approximate time until drift appears. Mention any decoder change that affects the result. Avoid posting private stream URLs. A precise sequence lets support reproduce the timing path more effectively than a screenshot, which cannot show a growing audiovisual mismatch.