502 Bad Gateway by Logging out

Try to reproduce the issue in an incognito browser window. If the issue persists, check the server error log.

An incognito browser window does not solve the problem. Here is the error log:

2021/03/11 20:06:26 [error] 2167#0: *7029557 upstream sent too big header while reading response header from upstream, client: 88.207.240.156, server: shop.kaerjeng.lgs.lu, request: “GET /aloggen/?action=logout&redirect_to=https%3A%2F%2Fshop.kaerjeng.lgs.lu%2Fkonto%2F&_wpnonce=e9206bd090 HTTP/1.1”, upstream: “https://46.4.80.166:7081/aloggen/?action=logout&redirect_to=https%3A%2F%2Fshop.kaerjeng.lgs.lu%2Fkonto%2F&_wpnonce=e9206bd090”, host: “shop.kaerjeng.lgs.lu”, referrer: “https://shop.kaerjeng.lgs.lu/konto/”

You need to update your NGINX configuration: https://ma.ttias.be/nginx-proxy-upstream-sent-big-header-reading-response-header-upstream/

Thank you very much, @gioni , this solved my same problem.