I actually have an avo tree taller than me that I started this way 10 or so years ago. It is in a pot, and our climate is a bit cold for them, so I move it into the house in winter.
These are normally outside, just hiding from the worst of the winter.
Could it just be a bit cold?
Unless OPs living space is constantly below ~15°C, it shouldn’t be an issue.
Oh i was just thinking like how rhododendrons droop their leaves in the winter,. If the avos could be doing a similar thing. But good to know!
Avocados originate from Mesoamerica where Winters are mild. They have no dormant period.