When I desynchro Formula Synchron but the monsters I used were not be special summoned.
Also when I desynchro Shooting Quasar Dragon, it should special summoned Shooting Star Dragon when it leaves the field, but it NEVER HAPPENED.
Please FIX this as soon as possible. And sorry if my English is bad. 😞

1. de-synchro only special summon a monster that was used for sycnhro summon from your graveyard.
2. de-synchro won't special summon monsters that have change place (ex: if you use shura and gale to make armor master then you use monster reborn to summon THAT gale, then when that gale goes to grave. it won't be special summoned by de-synchro.) source wikia 

If a Synchro Material Monster used in the Synchro Summon is removed from the Graveyard, it cannot be Special Summoned with "De-Synchro", even if it is returned to the Graveyard.

If a Synchro Material Monster(s) is removed from the Graveyard and then sent to the Graveyard again, then it is no longer considered a Synchro Material Monster(s) and you cannot Special Summon any monsters with "De-Synchro".

3. if that synchro monster already left the field at least once, de-synchro won't special summon the material. source wikia 

Suppose that a Synchro Monster is banished by "Interdimensional Matter Transporter" and then Special Summoned by "Return from the Different Dimension". If it is targeted by "De-Synchro", then you cannot Special Summon the Synchro Material Monsters from the Graveyard.

4. for shooting quasar's part. you won't get Shooting Star Dragon because of the misstiming. source pojo