Platforms: Windows 10 (64bit); Android 7.1 

When I have prizes from defeating the Clan Boss, and I try to sell them directly, I get an error. 

Windows:

I click on the item I won, and then I click sell

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Then, I get the following error, and the item is not sold. 

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I can continue, but then have to sell the artifacts from my inventory. 

The same happens on Android

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It's been happening over the last couple of weeks at least.