Intermittend build failure on CI (Windows)

On our Windows (Server 2016) CI build server, we see intermittent build failures like these:

[5/5] Building fresh packages...
Done in 175.06s.
node_modules\.bin\ember.cmd build --output-path ..\(...)\ --environment=development

Running without permission to symlink will degrade build performance.
See for details.

09:15:33 - Starting compilation in watch mode...

09:15:37 - Compilation complete. Watching for file changes.
cleaning up...
Cleanup error.
ENOTEMPTY: directory not empty, rmdir 'C:\VSTS\_work\32\s\(...)\tmp\funnel-output_path-Qcu26lv4.tmp'

I’m not quite sure what to make of this, as a subsequent build doesn’t run into the same issue. We’re using ember-cli-typescript, but I don’t know if that’s any relevant. We’re on ember-cli 3.0. Does anyone have any pointers on how to resolve this issue?