SFTP Receiver adapter issue in test environment

we are facing the below strange issues with SFTP receiver adapter very frequently in PO

These issue is not limited to one particular to SFTP server or Channel. This issue affecting all SFTP communications on our test environment. Please find the below list of issue that we face in our application more frequently.

• Send Failed : com.kcraft.jsch.JschException: Connection to SFTP server failed. The login credentials provided are incorrect.
• Send Failed :java.lang.Exception: directory does not exist.
• Send Failed : 2:pwd failed.
• Send Failed : Could not obtain resource within timeout

Request you all to provide suggestions to fix this issue.