Our picture for this phenomenon:



The E(4260) signal stems from radiation,
namely, of a f0 by the gluon cloud.

The inner part of the cc propagator
competes with a much faster process,
namely, open-charm decays.

The latter reaction depletes the E(4260) signal
in particular at
resonances and threshold enhancements.

   literature:
  hep-ph/0605317 (unpublished)
  arXiv:0904.4351 (unpublished)
  PRD79, 111501R
  arXiv:1005.1010