> potentially reducing the cost

Aren't we getting close to being safe to assume that this is actually true? They've already re-used a number of boosters. (:

Keeping video feed going during the landing is way, way, way, way, way, way down the priority list. The video gets recorded, so they don't need this for analysis. It's purely a promotional thing, which is fun, but saving five seconds of the stream (even if it's an important five seconds) is only worth so much effort.

No need for speculation - the feed never cuts out on the return-to-launch-site landings. It's only wonky on the ship landings.

Bouys bounce around a lot - the drone ships have special station-keeping thrusters to stay in place.

it's vibrations that shake the sat dish so much the link gets severed. convenient for them.

You're underestimating the shock waves those engines produce. During launches you see camera footage from miles away shaking as the engines go to full power.

Of course there are solutions, but they're all expensive, and SpaceX has better things to spend money on. It's not like the footage doesn't exist - we're just not getting it live.