Could you please instruct customer to configure Apache Tomcat to configure underlying Java to use en_US locale? It should look like this in Tomcat's configuration tool:
where relevant parameters are -Duser.country=US and -Duser.language=en.
This problem seems to affect only customers hosting ESMC Webconsole on Turkish Windowses. If this is the case, reconfiguration and Apache Tomcat service restart should be sufficient to resolve this issue.