This error can occur for multiple reasons. The most common of which include:

1. Incorrect use of weather effects with backgrounds. 
   • Do not include the word 'weather' next to effect:
     • Incorrect: INT. BACKGROUND with weather effect RAIN
     • Correct: INT. BACKGROUND with effect RAIN 
   • Don't forget to add 'with' before effect:
     • Incorrect: INT. BACKGROUND effect RAIN
     • Correct: INT. BACKGROUND with effect RAIN
2. Missing spot placement coordinate numbers