Subtitle synchronisation on C4


My wife is hard of hearing and relies on subtitles. We have no problems with BBC recordings. However, when playing back recordings of Homeland on Channel 4, frequently the subtitles are displayed well in advance of the action. Stop / resume normally brings them back in sync but it is not long before the fault returns. This is not a recent problem. Has anybody else had the same experience?
I've not noticed it on Ch4 but C5 (and 5USA) are terrible for it. It's usually when there is a pause in the speech while action is going on, but the subtitles keep on going.
In the past turning them off and on has resynched, but of late that hasn't worked, so I have to just turn them off for a while until there is something I really can't hear. Sometimes they will be resynched when I put them back on.
As you say, it seems to be some channels and not others, so I suspect it is poor control by the broadcasters rather than the box being at fault.
(Some programmes on 5USA - Longmire is one - aren't subtitled at all these days which is very poor as the first series was. I really must complain to someone about that.)