VMSS Custom script not fully executing - bash

Question

We are currently experimenting with new VMSS build agents for our devops environment, which requires some components for each build pipeline.
So to make sure don't need to add this to every build pipeline, we created a startup script which is executed every time the machine is created (standard custom script extension) with the following contents
#install kubectl
echo "Installing KubeCTL"
curl -LO "https://dl.k8s.io/release/$(curl -L -s https://dl.k8s.io/release/stable.txt)/bin/linux/amd64/kubectl"
sudo install -o root -g root -m 0755 kubectl /usr/local/bin/kubectl
echo "Installing DotNet SDK"
#install dotnet runtime (5) for dotnet tool install
sudo apt-get install -y dotnet-sdk-5.0
echo "Installing DotNet DotNet Runtime"
#install dotnet runtime (5) for FluentMigrator
sudo apt-get install -y dotnet-runtime-5.0
echo "Installing DotNet AzureCLI"
#install AzureCLI
curl -sL https://aka.ms/InstallAzureCLIDeb | sudo bash
echo "Installing Powershell"
#install powershell
# Update the list of packages
sudo apt-get update
# Install pre-requisite packages.
sudo apt-get install -y wget apt-transport-https software-properties-common
# Download the Microsoft repository GPG keys
wget -q "https://packages.microsoft.com/config/ubuntu/$(lsb_release -rs)/packages-microsoft-prod.deb"
# Register the Microsoft repository GPG keys
sudo dpkg -i packages-microsoft-prod.deb
# Update the list of packages after we added packages.microsoft.com
sudo apt-get update
# Install PowerShell
sudo apt-get install -y powershell
echo "Installing FluentMigrator"
#install fluent migrator
dotnet tool install -g FluentMigrator.DotNet.Cli
echo "Installing OpenJDK"
#install openJDK
sudo apt-get install -y openjdk-11-jre
Now, everything in this script executes and installs without any issues, the build pipeline runs correctly after a new agent is booted up.
However, during release time, we require fluentmigrator, which is not installed even though it is included in the script.
If we add the same install line dotnet tool install -g FluentMigrator.DotNet.Cli as a build step or as a step during release it gets installed correctly. To do this we run a custom bash with the command.
However, i would very much prefer to have this run within the boot-up of the machine instead of adding a custom bash script to 20 release pipelines. Anyone has any idea why the tool is not installing correctly within this script?