Special Characters introduced into the files when uploaded to SFTP using Blogical adapter

Question

We have a BizTalk 2009 solution which will fetch the files from FTP, do the processing and finally move to a SFTP .

We found the files recently moved to SFTP started getting some special characters.

for e.g. J¥§2qPTA |9Çô vœÅÖû}kky/A FÐíàw±\l«^6 Ý

We are using the SFTP Blogical.Shared.Adapters.Sftp.

How do we stop these characters from being introduced?