If visitors do not clear their browser cookies, they may receive a 502 error

If visitors do not clear their browser cookies, they may receive a 502 error.
Why is this?

If your website has been cached with cloudflare with the error then you may need to purge cache assuming the error is not there now. It depends what rules you have set up.

You can do so here:

It seems that the 502 error is caused not by cloudflare’s cache, but by the visitor’s browser cache and cookies. When the visitor cleared the cookies and cache, it became normal.