Alarms not added for containerized Lambda

[sarynik]

This is a Bug Report

Description

I am trying to add an alarm to a containerized Lambda_. I couldn't find any mention of whether this is officially supported
The deployment runs fine with no errors, but the alarms do not get created. I do not observe this issue with regular (non-containerized) Lambda functions.

The config is pasted below:

service: lambda-ecr-unoconv

provider:
  name: aws
  region: eu-west-1
  memorySize: 1024
  timeout: 900 #sec
  deploymentBucket:
    name: ${opt:stage}-serverless-deployment
  iam:
    role: ${ssm:/${opt:stage}-lambda-serverless-role-arn}
  ecr:
    images:
      appimage:
        path: ./

plugins:
  - serverless-plugin-aws-alerts

functions:
  main:
    name: ${opt:stage}-unoconv
    environment:
      INPUT_S3_BUCKET: ${ssm:/${opt:stage}-file-upload-bucket-name}
    image:
      name: appimage

custom:
  alerts:
    stages:
      - production
    topics:
      alarm:
        topic: ${ssm:/${opt:stage}-alarms-sns-arn}

Additional Data

• Serverless Framework Version: 2.71
• Stack Trace: No error thrown
• Provider Error messages: No error thrown