Mixer window doesn't save split position

Dorico
1
  1. press button on top to open mixer window
  2. adjust size of window - vertical/horizontal
  3. adjust split between “inserts/eq/sends” on top vs “volume” part on bottom.
  4. close mixer window
  5. press button again to open mixer window
  6. window horizontal/vertical size are preserved, but split between top and bottom is not, so split needs to be set again by clicking/dragging mouse.

Dorico 6.