is it just my TV that goes black during replays during the world cup?

Lucky

These issues typically occur in digital systems when the received signal strength is poor and barely passes

At high bitrate or with a spike in errors, or both, the video stream cuts out for a moment

See if there's anything you can do to improve the connection

If it's internet TV, and not a broadcast/cable connection then ignore me

It's a sign.

I've not had that happen on either Crave or TSN, which should be the same feed.

Experienced the same during the live streams in Norway because I currently have shit internet speeds.