Hi,
Can you paste the config from both sites to the post.
Also can you run the flow traceoption from site B to site A and attach it to the post.
Please paste the output of the below command too:
>show security match-policies from-zone <zone> to-zone <zone> source-ip x.x.x.x destination-ip x.x.x.x protocol <protocol number> source-port 23234 destination-port <dport>
Regards
Hemant