/var/lib/tomcat8/webapps is where application is deployed. But working directories for applications are in /var/lib/tomcat8/work/Catalina/localhost - try to delete them.

Best regards,
Victor

Thank You Victor, exactly like you write, after delete catalina work dir and start tomcat again new UI is up and running.

Problem solved.

Best regards,
Victor

i using tomcat8 on debian 10, so i stop it, delete working dir /var/lib/tomcat8/webapps

start it for test, so no web working, i copy downloaded .war from web into webapps folder, it been automaticaly deployed i see v3 libs in plugins directory, but web told me same is i posted before.
 :-
i do upgrade of previous versions using this method and was ok.

#!/bin/bash

wget -O ROOT.war https://www.netxms.org/download/releases/3.4/nxmc-3.4.284.war
chown tomcat8:tomcat8 ROOT.war
service tomcat8 stop
cp -f ROOT.war /var/lib/tomcat8/webapps
service tomcat8 start

Best regards,
Victor

For me it seems the web server still uses the old file. You could try recreating the config files and see if that help. If you are windows, you try to reinstall the webui service (webui installer).

Regards