A video call is fine until another device starts uploading photos. Your download speed test still looks respectable. The missing clue may be how long small packets wait while the connection is busy.
Measure responsiveness under load
Speed describes how much data can move over time. Latency describes delay. When queues grow during a busy transfer, an interactive task can become sluggish even though plenty of data is moving. Cloudflare’s Internet quality work includes latency under load because idle measurements leave out that experience.
Compare the same call or latency test with the upload paused and then active. Repeat briefly to see whether the relationship is consistent. Avoid treating one result as a diagnosis.
Separate the local radio from the internet link
If possible, make a comparison using a wired computer. That can help distinguish a Wi-Fi contribution from congestion elsewhere, though it does not isolate every part of the route. Check whether several devices show the same pattern.
Write down the conditions: active uploads, connection type and time. Those details are more useful than a single maximum speed number.
Try the smallest useful adjustment
Schedule a large upload outside a call or use the uploading application’s bandwidth limit where available. If considering router queue-management features, consult its documentation and save the existing settings first. Buying a faster plan or another access point without identifying the busy link can leave the original problem in place.