Duke3D: Polymer lights disappear after restarting the map after death
Pre-placed lights, e.g. SE49 and SE50 spot and point lights, or lights emitted by certain other sprites, disappear after the player dies and restarts the map.
They can be reactivated by typing
restartvid in the console.
Here's a test map: test5.map
(thanks to Francesco V. for finding this)