@mahadevb28593292As discussed, the issue was occurring because MS Excel was adding garbage  to the .tsv files. We were able to import the file in bulk editor effectively after editing it using a text editor such as notepad ++
The bulk importer was not correctly importing the value of .tsv file after it was being modified in MS Excel
We discovered that the MS Excel was adding some garbage  to the .tsv file thus breaking its format and as a reason of which bulk editor could not import the multi-string data effectively
Edit the .tsv file using a text editor such as notepad or notepad++ and it then import works fine for multi-string values as well.