Localized message pack warning during start-up

Hello,
We have noticed that on the deployed version of our application there are some messages and formats that are not being set correctly (as they are in the project). We have also noticed that during the start-up of our project we are getting the following warning:

Localized format strings are not defined. Check cuba.mainMessagePack application property, it must point to a valid set of main message packs.

We believe these two issues might be related. Is there any way to debug the start-up in order to get more information about what is causing these problems?
For context, these formats and messages are in the file:

modules/global/src/com/haulmont/cuba/core/messages_es.properties

and we have set the mainMessagePack in the following directories (according to app.properties and web-app.properties respectively):

  • Web: +com.company.helium.web
  • Core: +com.company.helium.core

Thanks beforehand,
T.

EDIT: When running it locally, we do not have this issue, it happens only when we try to deploy it onto a server.