Debug service stops consistently when run with --enable-expression-evaluation

Dart SDK version: 2.12.0-edge.d13eaddf97d60c706f8a8969a8998ab6b083f753 (be) (Thu Nov 5 15:17:43 2020 +0000) on "macos_x64"
webdev 2.7.1
analyzer 0.39.4

I got the application running, found a medium-sized file and was scrolling through it for an interesting place to put a breakpoint. It seems to stop consistently, the DevTools UI just says disconnected and the log says
[INFO] DevHandler: Stopped debug service on sse://127.0.0.1:53029/gJh9lrBkL7g=/$debugHandler

I can reproduce this, so I can probably get more information if I know how to turn on more detailed logging. I can also provide the pubspec.lock information. The context is a large application compiled with dart2js and a very small piece compiled with DDC, though it has some dependencies. When I first ran I had too many files open (only when I did enable-expression-evaluation). A ulimit -S -n 2048 (MacOs 10.15.6) fixed the files issue.

Reproduce the disconnect on macOS with the --enable-expression-evaluation option in the reported Dart SDK, webdev, and analyzer versions. Start by collecting more detailed logs around the stopped debug service; done means the service remains connected during the reported browsing and breakpoint workflow.

Written by the indexing model from the issue text.