AWS CodePipeline "The deployment failed because the AppSpec file that specifies the deployment configuration is missing ...." - amazon-web-services

Question

I'm trying to set up a deployment pipeline using CodeCommit, ECR and ECS. My pipeline passes the source and builds the image right, except for deployment phase, where it fails:
The deployment failed because the AppSpec file that specifies the deployment configuration is missing or has an invalid configuration. The input AppSpec file is a not well-formed yaml. The template cannot be parsed.
appspec.yaml is in the output of my build phase (stored inside a zip file in S3)
The following is my code pipeline:
{
"pipeline": {
"name": "dashboardpipeline",
"roleArn": "arn:aws:iam::410208438878:role/service-role/AWSCodePipelineServiceRole-us-east-2-DashBoardPipeline",
"artifactStore": {
"type": "S3",
"location": "codepipeline-us-east-2-276644567431"
},
"stages": [
{
"name": "Source",
"actions": [
{
"name": "Source",
"actionTypeId": {
"category": "Source",
"owner": "AWS",
"provider": "CodeCommit",
"version": "1"
},
"runOrder": 2,
"configuration": {
"BranchName": "master",
"OutputArtifactFormat": "CODE_ZIP",
"PollForSourceChanges": "false",
"RepositoryName": "provisions_dashboard"
},
"outputArtifacts": [
{
"name": "SourceArtifact"
}
],
"inputArtifacts": [],
"region": "us-east-2",
"namespace": "SourceVariables"
},
{
"name": "Image",
"actionTypeId": {
"category": "Source",
"owner": "AWS",
"provider": "ECR",
"version": "1"
},
"runOrder": 2,
"configuration": {
"ImageTag": "latest",
"RepositoryName": "dashboard-web-app"
},
"outputArtifacts": [
{
"name": "MyImage"
}
],
"inputArtifacts": [],
"region": "us-east-2"
}
]
},
{
"name": "Build",
"actions": [
{
"name": "Build",
"actionTypeId": {
"category": "Build",
"owner": "AWS",
"provider": "CodeBuild",
"version": "1"
},
"runOrder": 1,
"configuration": {
"ProjectName": "DashboardApplicationBuild"
},
"outputArtifacts": [
{
"name": "BuildArtifact"
}
],
"inputArtifacts": [
{
"name": "SourceArtifact"
}
],
"region": "us-east-2",
"namespace": "BuildVariables"
}
]
},
{
"name": "Deploy",
"actions": [
{
"name": "Deploy",
"actionTypeId": {
"category": "Deploy",
"owner": "AWS",
"provider": "CodeDeployToECS",
"version": "1"
},
"runOrder": 1,
"configuration": {
"AppSpecTemplateArtifact": "BuildArtifact",
"AppSpecTemplatePath": "appspec.yaml",
"ApplicationName": "dashboarddeploymentapp",
"DeploymentGroupName": "dashboardappdeploygr",
"Image1ArtifactName": "MyImage",
"Image1ContainerName": "IMAGE_URI",
"TaskDefinitionTemplateArtifact": "BuildArtifact",
"TaskDefinitionTemplatePath": "taskdef.json"
},
"outputArtifacts": [],
"inputArtifacts": [
{
"name": "BuildArtifact"
},
{
"name": "MyImage"
}
],
"region": "us-east-2"
}
]
}
],
"version": 18
},
"metadata": {
"pipelineArn": "arn:aws:codepipeline:us-east-2:410208438878:dashboardpipeline",
"created": "2022-03-14T11:52:19.525000-03:00",
"updated": "2022-03-18T11:34:14.217000-03:00"
}
}