Progress bar background changes between first and subsequent playlist items

When the player first loads (with the first video in the playlist), the colour of the progress bar (the right-hand, unplayed section) is defined by:
<div class="minplayer-default-progress ui-state-default" style="width: 100%;"></div>
This picks up the colour from ui-state-default in the chosen preset theme.

However, when subsequent playlist items are selected, the width of this div is set to 0%:
<div class="minplayer-default-progress ui-state-default" style="width: 0%;"></div>
The colour of the progress bar therefore displays as the background colour of the enclosing div, which uses the default for the osm player.

This isn't very visible in most of the standard (pre-installed) themes, but just happens to be very noticeable on my custom theme!