Hi Sam
Thank you for your question.
If this is a windows LMT server then exit code 41 workaround is stated as below:
https://www.ibm.com/support/pages/upgrading-latest-ilmt-version-windows-failed-fixlet-exit-code-41
For the current exit code 55, it indicates All elements of the infrastructure are already installed.
Its best to raise a salesforce case to ILMT Support so we can check into the registry files for ILMT.
Thank you
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