Fixed: changeset/175892606

@GinaroZ I've posted some analysis here:
@jwheare/diary/407915

I'll fix my edits to remove the duplicate leisure tagging.

Thank you for checking my edits. The tagging of slipways seems quite non-standard.

The recommended approach seems to be to tag the way as highway:service service:slipway and the final node should be leisure:slipway

From leisure=slipway

"The highway=service that is part of the physical slipway is often further refined with a service=slipway. Keep in mind though that this does not replace leisure=slipway, mapped as a node on the end of that way."

I think what's causing the visual duplication on the map is the leisure=slipway attached to this way which should potentially be removed, leaving it on the node only:
way/436559271

But there are multiple approaches that people seem to take. What would you recommend?