Maps showing gray dashes

The map has weird, gray markings on it that look like small ravines... I've attached a picture of what it looks like. This only started happening after the snapshot 20w17a, I've had these maps in an item frame and took them out to map something new that I built, and that's when the markings appeared. If I could please get some help on how to fix this, or just be informed that this is happening because of a bug with the snapshot, I would be extremely thankful.