Stripe on screen

Hi glyderfach,

Does this happen even after a restart? Shut down or restart your Mac - Apple Support

If so, it looks like your MacBook may need service as this appears to be a Hardware issue.

You may contact Apple here: Contact Apple for support and service - Apple Support

Cheers!

Hi glyderfach,

Thanks for using Apple Support Communities. We see you are experiencing an issue with your Mac display and recommend starting with the steps to resolve display concerns here: If your Mac display doesn’t look right - Apple Support

Thanks

You still might want Apple to evaluate it. A water incursion is most insidious as you can count on corrosion having already started. Home remedies many times lead to the same inevitable outcome: a trip to Apple.

Corrosion takes time, and the sooner you get corrosion mitigated the better. But, it's your call obviously.