Warning: could not determine a source map reference

Using sentry-cli to upload sourcemaps.
Commands are as follows:
sentry-cli releases -o expel -p ember-ui new (APP_VERSION) sentry-cli releases -o expel -p ember-ui files (APP_VERSION) upload-sourcemaps /app/build/assets

javascript file is:
expel-94fbb840f3e79898c381470ae1a15d60.js
at the bottom it has:
//# sourceMappingURL=expel-3e342dc6a903433419a2cf798a72a66d.map

I upload a map file with exactly that name. the sourcecode is inlined in the map.

What more do I need to be doing there :)?

build output:
Source Map Upload Report
Minified Scripts
~/expel-887ec517b9a71ec79a11cea02b03f096.js (sourcemap at expel-1f5b82f8f5ba1c03b50b4a93e75cb770.map)
- warning: could not determine a source map reference (Could not auto-detect referenced sourcemap for ~/expel-887ec517b9a71ec79a11cea02b03f096.js.)
~/vendor-693d27de4df6bf69ad288ecce5f1b67f.js (sourcemap at vendor-57a4ad5e6c50dfdd4084e46f2628fc37.map)
- warning: could not determine a source map reference (Could not auto-detect referenced sourcemap for ~/vendor-693d27de4df6bf69ad288ecce5f1b67f.js.)
Source Maps
~/expel-1f5b82f8f5ba1c03b50b4a93e75cb770.map
~/vendor-57a4ad5e6c50dfdd4084e46f2628fc37.map