The error 502 means The server is currently unavailable (because it is overloaded or down for maintenance). Generally, this is a temporary state.
I recommend you to check your Confluence connections. Looks like your proxy is trying to communicate to Confluence, but Confluence is too busy to reply.
These links can be useful:
Hi my Community friends! For those who don't know me, I'm a product marketer on the Confluence Cloud team - nice to meet you! For those of you who do, you know that I've been all up in your Co...
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