Problems with (I think) the language server and maven cross-project dependencies

This is possibly a PEBCAK or user-ignorance issue.

I work with several Maven projects.
I have project A and project B open in separate VSCOde workspaces. Project B has multiple sub-projects

A subproject of Project B builds a JAR that is a maven dependency in project A.

Project B is quite large. Project A is small (but all are spring boot so there's quite a lot of cruft around).

If in project B I make some change (say, add a method to a class) and "mvn install", then the VSCode doesn't pick up the change in project A. The new method isn't visible.

Java: refresh, Java: force compilation, java: update project configuration don't fix this.
Java: clean the language server workspace sometimes fixes it, but not always. And takes an age so I don't want to be doing this.

The dependencies are all correct as far as Maven is concerned, as a command-line "mvn install" (for example) of Project A succeeds, including the code that calls the new method

Existing the VSCode for Project A and restarting does seem to work, so it looks like some sort of refresh/caching issue

How am I supposed to set things up for this case? (one maven project depending on the artefact of another)?

I've tried adding Project B as a folder to the workspace of Project A - but the LSP seems to have issues with that (I previously reported a non-reproducable bug were @Test run/debug no longer appeared, and when I tried it as a work around for this, I lost the semantic highlighting etc, (I think - the import statements weren't green but white, as they are while the LSP workspace is loading when first opening the workspace).

If I can provide more info/logs etc, please let me know what is needed.

Environment

• Operating System: Windows 10
• JDK version: VSCode says current version is JDK11
• Visual Studio Code version: 1.47
• Java extension version: MS Java 0.9.1, Redhat 0.65.0

Steps To Reproduce

Please see description above, I don't have a small test case. Sorry

[Please attach a sample project reproducing the error]
Proprietary code. I can't.
Please attach logs

Current Result

Expected Result

Additional Informations

No se proporciona ningún archivo fuente, prueba ni reproducción pequeña. Empieza siguiendo el escenario de Maven con dos workspaces del issue en Windows, con las versiones de Java y de la extensión indicadas, y después habilita los language-server logs mediante la guía de troubleshooting enlazada. Se considera terminado cuando los cambios instalados desde Project B pasan a ser visibles en Project A sin reiniciar VS Code ni limpiar el workspace del language server.