<p>Yes specifically this is cause by passing an invalid client key that doesn't match any known client, or possibly also a request with an invalid signature.</p>
<p>It's primarily a user error and while a 500 is not a good response it is as <a class="user-mention" data-hovercard-type="user" data-hovercard-url="/hovercards?user_id=5842757" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://github.com/mmd-osm">@mmd-osm</a> says largely outside our control. I believe there are also other tickets already open for this.</p>

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