Non-deterministic behaviour of MultiZarrToZarr

[TomNicholas]

I'm seeing what looks like non-deterministic behaviour with MultiZarrToZarr. It happens both with and without writing to parquet. Sometimes I get the expected result written, sometimes I don't. See the standalone notebook here.

I'm also seeing different behaviour when I do/don't write out to parquet. Even the act of writing to parquet is changing the json returned by MultiZarrToZarr.

(The example in the notebook comes from a snippet I created whilst trying to work around the bug reported in #386 - see #386 (comment). It's slightly odd because I preprocess then postprocess in the same MultiZarrToZarr call. But that should be a perfectly well-defined thing to do.)

This behaviour might be specific to the application of preprocess and postprocess, but it also might be indicative of a more wide-reaching bug.

I am hoping I am somehow using MultiZarrToZarr incorrectly, but given how I'm running identical code in consecutive cells and seeing different behaviour, I don't understand how this can be user error.