Looking into my wood flute one day and seeing a forest of green and brown hairy things growing inside made me cringe. I did a lot of research and eventually used Tea Tree oil, with excellent results. The mold was gone for good within a week, and the Tea Tree aroma dissipated completely within 4 weeks.
However, there are caveats ...
I have added recommendations regarding Tea Tree oil to my page on Flutopedia - see the bottom of this page:
https://www.flutopedia.com/care.htm
I'm hoping someone from Aodyo can respond ...
Is it OK to use one or two drops of Tea Tree oil in the Sylphyo?
Also, see cautions on that Flutopedia page about possible allergic reactions.
As an alternative to placing a drop or two of Tea Tree oil directly into the Sylphyo, you could use a diffuser. You place a drop or two of tea tree oil on an medical swab (not a Q-tip, which can leave lint) and suspend the medical swab inside the bore of the instrument. The fumes of the Tea Tree oil provide the antifungal action. I believe that WoodSounds Flutes distributes a product specifically for this purpose