If you don’t know where or when the dog will drop or there are problems with the cued drop, your best bet is to freeshape and capture the drop.
Just wait for the dog to drop the disc. No cue, no prompting just wait. Observe the dog and capture the moment she takes her teeth off the toy.
When the teeth come off, mark then reinforce with a bite on the disc in hand if the drop needs to happen closer to the handler, or a nice long roller if the dog should drop the disc further away.
The endgame of this exercise is an immediate drop of a caught disc. Be careful, you can go from no drop at all to an immediate drop in a few sessions.