The plugin does not work with docker

[Saddamus]

I build docker image with multiple plugins, basing on etherpad dockerfile:
https://github.com/ether/etherpad-lite/blob/develop/Dockerfile
, but this one does not work for docker.
There are no errors on building - looks like module is installed, same as all others, but after starting docker instance it does not load, neither exist in node_modules
If i enter running docker etherpad instance as root and run command npm i ep_table_of_contents it will be installed and if i commit the image on docker level (after installation) and restart to commited container, module is loaded and works. It looks like it needs to be installed on running instance.
As there are no errors while building from Dockerfile, i dont know why it can not install that way.