SSH Executor fails before cloning with "Illegal variable name."

Hello,

In order to bypass issues with the shell executor (no TTY, even when using script, causes the tool under test to fail), I'm looking into the ssh executor. Here's the output:

Running with gitlab-ci-multi-runner dev (HEAD)
Using SSH executor...
<SSH server MOTD>
Illegal variable name.
ERROR: Build failed: Process exited with: 1. Reason was:  ()

The exact same build, with the executor set to shell:

Running with gitlab-ci-multi-runner dev (HEAD)
Using Shell executor...
Running on <machine name>...
Cloning repository...
Cloning into '<clone path>'...
Checking out 304bde42 as improve_ci...
<build goes on>

I've started gitlab-ci-multi-runner in debug mode, there's nothing helpful in the logfile.

Since I have the server's MOTD, I know that the connection is working fine. Is there a way to see the Bash script generated by gitlab-ci-multi-runner?

Thanks,

Clément