I see that there are certain scenarios where the issue has been fixed already, so try installing the latest Core Fix 4 (readme) on a sandbox or lower environment and test if the issue goes away -
PIE-79278 (IS_10.15_Core_Fix3)
The “pub.client:ftp” service throws the “Implicit FTPS is not supported” error
message when an invalid proxy alias is passed in the input, which is incorrect.
This issue is resolved. Now, the service throws “Could not connect to ftp
server”.
PIE-78418 (IS_10.15_Core_Fix1)
The pub.client.ftp:login service throws a NullPointerException while using the
FTPS protocol in the implicit mode.
Implicit FTPS is deprecated and Integration Server does not support the FTPS
protocol in the implicit mode. Hence, the service returns a
NullPointerException.
The issue is now resolved. The NullPointerException is now replaced with the
“Implicit FTPS is not supported.” message.
Observation -
Now, this last snippet above says that implicit FTPS is deprecated and IS does not support FTPS in the implicit mode.
However, since you say you use “FTP”, I assume it’s an incorrect error message, so try installing the latest fix and you should get the actual error message - possibly an intermittent disconnect from the IS (client) side.
KM
#Integration-Server-and-ESB#ftp#webMethods