Hi Dem,
From your logs we can say there is no issue at source side.
problem at BW side only.
All records sent to bw from ECC. But not received.
that means BW ports are not configured properly.
please ask basis to team check RFC configurations at SM59,
partner profiles at WE05 and WE20.
Tables - RSLOGSYSMAP and RSLOGSYSDEST.
above tables need to have source and target entries properly.
From BW rsa1-->source syste-->test connection and check it.
its basis probelm, they need to rectify it. please inform them.
Thanks