@jz68,

Defintely strange. I think this is a result of the filters those forums have placed for security reasons.

I would first try changing your DNS server to a common service, such as Google or Cloudflare, as this will change the route your traffic will take to reach its destination.

I would also recommend reaching out to the moderators of one of the forums, as they may be able to provide more information about why your posts are being automatically blocked.

Has this also been happening for a longer period of time? It could be that your forums are looking at your network properties or IP address to help determine if it is an unusual login attempt, and these had changed when exchanging equipment.