What are these hundreds of horizontal lines?

After these lines appear, the S-1 image that show up right after is extremely bright in that area (i.e. we cannot see anything).

Help?

This is the openstreetmap style: the symbol you are referring to is wetlands, so I assume that is the land cover type. https://www.openstreetmap.org/key

How do I change it back to normal Sentinel-1 data? That is how to change land cover type?

This is just a basemap, so just to give you the user a sense of where you are geographically when using EO Browser. This link will take you back to a Sentinel-1 visualisation: https://sentinelshare.page.link/X9sT