WinSCP failing to connect to FTP most (not all) of the time, just says "Connection Failed"
This started about 2 days ago. We have multiple scripts connecting to an FTP site and then syncing various folders and files. It uses WinSCP.com and an .ini file for the saved site configuration. The scripts are running on a windows server, using WinSCP version 5.13.3. It does succeed about 1/3rd of the time (including retries), so I don't think the issue is with the scripts themselves (or else they wouldn't succeed on retry). Logs are below, some identifying information has been replaced with {removed}. If nothing else, I'd like to figure out how to get some more detailed error information other than "Connection Failed". Or can any information be gleaned from the fact that we're not seeing something more specific?
. 2020-01-09 04:25:03.878 --------------------------------------------------------------------------
. 2020-01-09 04:25:03.878 WinSCP Version 5.13.3 (Build 8565) (OS 10.0.14393 - Windows Server 2016 Datacenter)
. 2020-01-09 04:25:03.879 Configuration: c:\integrationfiles\shared\ftpconfigs.ini
. 2020-01-09 04:25:03.879 Log level: Normal
. 2020-01-09 04:25:03.879 Local account: {removed}
. 2020-01-09 04:25:03.879 Working directory: C:\Program Files (x86)\WinSCP
. 2020-01-09 04:25:03.879 Process ID: 16612
. 2020-01-09 04:25:03.880 Command-line: "C:\Program Files (x86)\WinSCP\WinSCP.exe" /console=5.13.3 /consoleinstance=_13532_930 "/ini=c:/integrationfiles/shared/ftpconfigs.ini" "/console" "/script=c:/IntegrationFiles/{removed}/ftpParam.txt" "/log=C:/IntegrationFiles/Shared/winSCPLogs/{removed}.log"
. 2020-01-09 04:25:03.880 Time zone: Current: GMT+0 (Coordinated Universal Time), No DST
. 2020-01-09 04:25:03.880 Login time: Thursday, January 9, 2020 4:25:03 AM
. 2020-01-09 04:25:03.880 --------------------------------------------------------------------------
. 2020-01-09 04:25:03.880 Script: Retrospectively logging previous script records:
> 2020-01-09 04:25:03.880 Script: open vpFTP
< 2020-01-09 04:25:03.880 Script: In scripting you should not rely on saved sites, use this command instead:
< 2020-01-09 04:25:03.880 Script: open ftp://{removed}
. 2020-01-09 04:25:03.880 --------------------------------------------------------------------------
. 2020-01-09 04:25:03.880 Session name: vpFTP (Site)
. 2020-01-09 04:25:03.880 Host name: {removed} (Port: 21)
. 2020-01-09 04:25:03.880 User name: {removed} (Password: Yes, Key file: No, Passphrase: No)
. 2020-01-09 04:25:03.880 Transfer Protocol: FTP
. 2020-01-09 04:25:03.880 Ping type: Dummy, Ping interval: 30 sec; Timeout: 15 sec
. 2020-01-09 04:25:03.880 Disable Nagle: No
. 2020-01-09 04:25:03.880 Proxy: None
. 2020-01-09 04:25:03.880 Send buffer: 262144
. 2020-01-09 04:25:03.880 UTF: Auto
. 2020-01-09 04:25:03.880 FTPS: None [Client certificate: No]
. 2020-01-09 04:25:03.880 FTP: Passive: Yes [Force IP: Auto]; MLSD: Auto [List all: Auto]; HOST: Auto
. 2020-01-09 04:25:03.880 Local directory: C:\IntegrationFiles\, Remote directory: home, Update: No, Cache: Yes
. 2020-01-09 04:25:03.880 Cache directory changes: Yes, Permanent: Yes
. 2020-01-09 04:25:03.880 Recycle bin: Delete to: No, Overwritten to: No, Bin path:
. 2020-01-09 04:25:03.880 Timezone offset: 0h 0m
. 2020-01-09 04:25:03.880 --------------------------------------------------------------------------
. 2020-01-09 04:25:03.881 Connecting to {removed} ...
. 2020-01-09 04:25:03.886 Connection failed.