BSEG is one of the largest table and is cluster table of RFBLG., these type of tables need tobe replicated with special settings in LTRS tcode in SLT system.
you can refer How to improve the initial load especially the section "Which Process Should You Use To Load Large Tables?"
or you can also enable "replication logging" but this will consume some space on SLT system.
note:- make sure all the relevant DMIS notes are applied on SLT server for respective patch level.
Regards
Kishore