A bit tricky one to reproduce, we are actively using this plugin and don't see this on our Jenkins servers, and probably could be due to Jenkins and plugin combination.

Can you provide more information? like what is FileName is? Nothing pops up to me, can you make sure into: FileName is string vs a variable ? like into: "abc.txt"

Not sure if this will format correctly, but hopefully gives you enough of an idea:

import java.text.SimpleDateFormat

node {
def dateFormat = new SimpleDateFormat("yyyyMMddHHmm")
sourcefile="server.log"
String partialFileName = "
" + sourcefile + "${MAL}" + dateFormat.format(new Date()) + "soc"

servers = ['10.xxx.xxx.xxx',]

def soc_remote = [:]
soc_remote.name = "${MAL} SOC"
soc_remote.allowAnyHosts = true
soc_remote.fileTransfer = 'scp'

withCredentials([usernamePassword(credentialsId: 'Credentials', usernameVariable: 'USER_ID', passwordVariable: 'USER_PASSWORD')]) {
soc_remote.user = USER_ID
soc_remote.password = USER_PASSWORD

servers.each { server ->
String FileName = partialFileName + server + ".txt"
echo "${FileName}"
soc_remote.host = server

stage("Run log gather script on ${server}") {
sshCommand remote: soc_remote, command: "ls -ltr /srv/jboss/server/${MAL}/log/${sourcefile}"
}
stage("Download ${MAL} logs from ${server}") {
dir("D:\\Logs\\${MAL}\\logs
${server}") {
try {
def commandResult = sshGet remote: soc_remote, from: "/srv/jboss/server/${MAL}/log/${sourcefile}", into: FileName, override: true
} catch (err) {
echo "something failed"
echo "${err}"
}
}
}
}
}
}

you could use the code block in JIRA for formatting. Like

import java.text.SimpleDateFormat

node {
    def dateFormat = new SimpleDateFormat("yyyyMMddHHmm")
    sourcefile="server.log"
    String partialFileName = "" + sourcefile + "${MAL}" + dateFormat.format(new Date()) + "soc"
    servers = ['10.xxx.xxx.xxx',]
    def soc_remote = [:]
    soc_remote.name = "${MAL} SOC"
    soc_remote.allowAnyHosts = true
    soc_remote.fileTransfer = 'scp'

    withCredentials([usernamePassword(credentialsId: 'Credentials', usernameVariable: 'USER_ID', passwordVariable: 'USER_PASSWORD')]) {
        soc _remote.user = USER_ID
        soc_remote.password = USER_PASSWORD
        servers.each { server ->
            String FileName = partialFileName + server + ".txt"
            echo "${FileName}"
            soc_remote.host = server
            stage("Run log gather script on ${server}") {
                sshCommand remote: soc_remote, command: "ls -ltr /srv/jboss/server/${MAL}/log/${sourcefile}"
            }
            stage("Download ${MAL} logs from ${server}") {
                dir("D:\\Logs\\${MAL}\\logs${server}") {
                    try {
                        def commandResult = sshGet remote: soc_remote, from: "/srv/jboss/server/${MAL}/log/${sourcefile}", into: FileName, override: true
                    } catch (err) {
                        echo "something failed"
                        echo "${err}"
                    }
                }
            }
        }
    }
}

Okay couple of things: 

• is the actual server that this step is trying to get the file from linux machine? 
• Not sure def CommandResult is causing this issue, can we delete that assignment and see if that is the cause.
• Looks like you are running Jenkins on Windows, unfortunately I didn't test this plugin on windows server, can you able test it on linux agent to see if that is the problem 

Yes, the remote server that it is getting the file from is a linux server, the source Jenkins server is Windows 2012
I actually added the def CommandResult as part of troubleshooting but i took it out again and get the same results
I am using a work provided Jenkins instance; not sure i have access to a linux box to install Jenkins on.

I don't have windows machine to test this right now, probably it might take more time for to me troubleshoot on this issue.

Ok, I spun up a micro instance on Google Cloud with Ubuntu and installed a fresh copy of Jenkins. I then took my pipeline and had it scp a file from that Jenkins server to that Jenkins server (didn't have anything else I could connect to). I attached the console log - it is still putting the contents of the file into the log itself. Code I used below, log is attached.

node {
 [^consoletext.txt]     sourcefile="test.txt"

servers = ['localhost',]

	def soc_remote = [:]
	soc_remote.name = "SOC"
	soc_remote.allowAnyHosts = true
	soc_remote.fileTransfer = 'scp'
   
	withCredentials([usernamePassword(credentialsId: 'Credentials', usernameVariable: 'USER_ID', passwordVariable: 'USER_PASSWORD')]) {
		soc_remote.user = USER_ID
		soc_remote.password = USER_PASSWORD
			
		servers.each { server ->
            String FileName = "test.txt"
            echo "${FileName}"
            soc_remote.host = server
				
				stage("Run log gather script on ${server}") {
					sshCommand remote: soc_remote, command: "ls -ltr /tmp/test/${sourcefile}"
				}
				stage("Download logs from ${server}") {
					dir("/tmp/") {
                        try {
                        sshGet remote: soc_remote, from: "/tmp/test/${sourcefile}", into: FileName, override: true
                        } catch (err) {
                          echo "something failed"
                          echo "${err}"
                          }
					}
				}
        }
	}
}

Apparently I didn't read your code fully before sorry about that.
It is probably you are using the 'scp' as a fileTransfer mode, try to remove that line so that it is going to fall back to sftp or set it to 'sftp'

...
soc_remote.fileTransfer = 'scp'
...