DuckDB (on Java) produces different results on Linux vs. MacOS vs. Windows?

[manticore-projects]

Greetings,

please see https://github.com/starlake-ai/jsqltranspiler
We have a test suite of 600 very simple, self containing SQL tests, which we verify against static expected results.

This test suite works reliable on Linux, different machines.
But a few tests fail reliably on Windows or MacOS, even with the following explicit properties:

    Properties info = new Properties();
    info.put("old_implicit_casting", "true");
    info.put("default_null_order", "NULLS FIRST");
    info.put("default_order", "ASC");
    info.put("memory_limit", "1GB");

What can cause such a different behaviour please?