The static mesh issue described in T65816 has been resolved by @Sergey
in T60094.
This commit fixes the last bit of the puzzle, which was two-fold:
- A missing depsgraph update when setting `orig_object.data = new_mesh`
from Python. Thanks @Sergey for providing the fix :)
- Properly locking the interface while exporting. This prevents crashes
as described in T60094. The previous approach of calling
`BKE_spacedata_draw_locks()` was not enough.
a9a8eedd16