In this changeset and in some related changesets you have deleted parts of the waterway network within the lake, e.g. this: https://pewu.github.io/osm-history/#/way/444775826

What problem were you trying to solve?

There are bunch of unconnected waterways now. I believe ways like this need to restored to keep the waterway network intact.

See also related Osmose report:
https://osmose.openstreetmap.fr/en/issues/open?item=1220&class=3&country=estonia