Hello,
Unity is giving several warning about DestroyImeediate when reimporting a texture for an already existing sprite in Editor.
It is asking to put "true" in DestroyImmediate if object destruction is required (to prevent asset destruction).
Concerned lines are in tk2dBaseSprite.cs :
line 300
line 304
line 306
Should be changed to :
DestroyImmediate(theObject, true);