Router uses wrong base url when deploying using a context path

[Artur-]

1. Download project from start.stg.vaadin.com using "TypeScript + Spring Boot"
2. Add server.servlet.context-path=/foo to src/main/resources/application.properties
3. Change /dashboard route to /dash/board in frontend/index.ts
4. Remove ...serverSideRoutes from frontend/index.ts
5. Run using mvn
6. Open http://localhost:8080/foo/dash/board

Expected:
Dashboard view is shown

Actual:

Uncaught (in promise) Error: [Vaadin.Router] Page not found (/foo/dash/board)
    at getNotFoundError (vaadin-router.js?6718:154)
    at eval (vaadin-router.js?6718:1834)

[Artur-]

If you edit the menu to link to dash/board instead of dashboard, then you can open http://localhost:8080/foo/masterdetail and navigate to dash/board by clicking BUT a refresh then results in the same exception

[Artur-]

When you open http://localhost:8080/foo, then
router.__effectiveBaseUrl is `"http://localhost:8080/foo/"

on the other hand, when you open http://localhost:8080/foo/dash/board then
router.__effectiveBaseUrl is "http://localhost:8080/"

Feels a bit like the relative base url is applied twice