The Form 1+ mirrors require special care to maintain functionality. Luckily all you need to know about inspecting them can be found here.
WARNINGExercise extreme caution when the mirror is exposed. Contact Customer Support before you clean your mirror or if you have any questions.
1. Remove the build platform and resin tank
2. Check the mirror for dust and resin
Without the right lighting, some dust or oils on the mirror may be impossible to see. Move your light source around to inspect the mirror at various angles.