First I dug around on your ISP's support site.
The ports blocked are Yes, port 25, 135-139, 445.Second, whats a TP-5? At some point there has to be something between the ethernet your plugging into the router and the fiber out on the street. The question is what? A ONT? If you connect the ethernet from the wall directly to the server/PC your trying to open the ports to, does it work?
Third, I did a common
port scan and got:
21 ftp An operation was attempted on something that is not a socket 85.230.51.212:21 0
22 ssh Success 156
23 telnet Thread was being aborted. 0
25 smtp Thread was being aborted. 0
53 dns Thread was being aborted. 0
80 http Thread was being aborted. 0
110 pop3 Thread was being aborted. 0
143 imap Thread was being aborted. 0
139 netbios Thread was being aborted. 0
389 ldap Thread was being aborted. 0
443 https Thread was being aborted. 0
587 msa-outlook Thread was being aborted. 0
1352 lotus notes Thread was being aborted. 0
1433 sql server Thread was being aborted. 0
3306 my sql Thread was being aborted. 0
3389 remote desktop Timeout 0
8080 webcache Timeout 0
The error "An operation was attempted on something that is not a socket" seemed to stand out. So I figured you probably have a server hooked up with MS Server on that IP, so tried MS Support and got
this article.So my gut is telling me it has something do to with how the server is configured you have on that 192 IP. ISP is allowing it to their end point, end point is routing to DIR-600L, your forwarding rule routes traffic to 192, but server application on computer using 192.168.2.40 isn't configured correctly. Thats why you get a different error when you remove the forwarding, because you are no longer reaching your server, so there for the response you got before the removal of the forwarding rule was FROM your server. Thats why the router doesn't record a error, because it doesn't see it as a error.
Do you have some routing somewhere, probably on the server, that points to different IP the old router gave you? My best guess is that has to be updated and your internal ARP cleared.
I feel Im still missing something. But that's my best guess with the data given.