I have both my TV and iMac hardwired to my fibreoptic router/modem.

When I stream video from Amazon Prime, it plays perfectly on my iMac, but audio/video isn't synchronised when I use the TV to stream from the same site.

The TV is closer to the router than the iMac (which is upstairs).

Playback from other services is fine.

Can someone explain why this is the case, please?  I don't use it very often, but would like to, from time to time.

Thank you.