>> This might be relevant to your case:
>> https://music.stackexchange.com/questions/141067/lilypond-to-musicxml
>
> indeed, that looks like it's the problem, since I'm also using
> OLL. However, I'm not using *this* function, but several others from
> OLL. How do I track down which is the problem? Or, better yet, is
> there an updated set of OLL libraries I can install somewhere to use
> instead?
Since Urs became sick and was no longer able to take care of OLL,
nobody jumped in to continue his work. This was and still is very
unfortunate.
Werner