Adding java agent on Tomcat 8

I am having trouble adding the Java agent to Tomcat 8 running in docker. This is the exception I get:

Error opening zip file or JAR manifest missing : /usr/local/tomcat/apm/elastic-apm-agent-1.16.0.jar
Error occurred during initialization of VM
agent library failed to init: instrument

I have checked that the jar file is there and have read permissions.
It is the same error I get if I remove the file, so clearly the file is not visible by Tomcat.

This is my file:
export CATALINA_OPTS="$CATALINA_OPTS -javaagent:/usr/local/tomcat/apm/elastic-apm-agent-1.16.0.jar"

This is from my Dockerfile:

ADD ./lib/elastic-apm-agent-1.16.0.jar /usr/local/tomcat/apm/elastic-apm-agent-1.16.0.jar
ADD ./lib/ /usr/local/tomcat/bin/
RUN chmod +x /usr/local/tomcat/bin/

It is running tomcat:8.5 (Have tried multiple images)

I am really stuck, so any help would be great.