Updates : Issue reappeared but atleast I am with workaround now. Will be placing wp_sitemeta update query for “illegal_names” in cron and then need to figure at what instance its making multiple entries for “illegal_names” with same site_id [site_id “1” in my case. I am changing site_id to “0” for duplicate entries]. Please make sure to exclude original / required sites meta_id during this operation.
Hope this will help someone to fix the issue temporarily or till I come back with proper fix.
RAM change didn’t helped much but I fixed the issue. Issue was with wp_sitemeta table, it was containing approx 6000 copies of same banned_name entries for site_id “1” and thus mysql was returning huge amount of data in response causing php to fail in handling it. Have updated site_id as “0” for other entries and kept original entry as it is.
Check with your wp_sitemeta table for site_id and banned_names.
Updates: I used developer tool to dig more into it and observed 500 internal error in response. It indicates must be something going wrong with database connectivity. Then I observed WordPress php error logs and it was telling me that whenever user clicks on register button, mysql client is running out of memory. I will be changing RAM by tomorrow and will check if that fixes it.
