How to remove non breaking space from body/value in migration process?
By taking a look into the StrReplace class I see that you are missing the source key, which should be the name of the field/column/whatever you are importing from.
If it does not work, try to also remove the &quot;regex&quot; key and if it still does not, try to use a simpler search, to ensure that the problem does not lie with your data.