Demonstration

https://codesandbox.io/s/systemjs-ignored-import-maps-j5xcl

Expected Behavior

Be aware of updates to any import map for later use of System.resolve() (for System.set()).

Actual Behavior

Only the first call to System.prepareImport() will parse import maps.

Possible Solution

Use MutationObserver to pick up any changes to script[type=systemjs-importmap], which might denecessitate prepareImport().