The Bravo robotic arm is only physically capable of holding one disc at a time. However, there are a few things that would cause discs to stick together.
New Media. New media taken directly from its packaging will often stick together. This happens because the printable surface that is applied to the discs before they are packaged was not completely dry. It is possible to pick up a stack of 100 discs and have 25 stick together at one time. To prevent this from happening, shuffle the media before you place it in the bin to make sure none of it is sticking together. The Bravo II and BravoPro have safe guards built in that check if more than one disc was picked. However, the Composer and Bravo have no such safe guards. If two discs are picked in these machines it can cause damage to the disc drive.
Static Electricity. Static electricity can also cause media to stick together in dry environments. This problem is especially noticeable if you have more than one media brand or type in the bin at the same time. At the point where the media transition occurs it is likely that the 1st brand of media will be statically attracted to the second brand of media. To prevent this, avoid mixing media brands and run the Bravos and Composers in a climate controlled environment.
Preprinted Discs. If you print your discs before you burn them and if the media was not fully dry when it was stacked, the ink from the top of one disc may stick to the bottom of another. This doesn't cause noticeable problems with the print quality but it can cause the discs to stick together.