I use Opera as one of a number of browsers for testing purposes. Noticed that Flash was jumpy (Opera 12.16 with flash 11.2 r202 on Ubuntu 14.04 64 bit). It took a while to find the problem but I believe that it was due to multiple flash plugins enabled. To see what plugins are enabled go to,

Opera -> Page -> Developer Tools -> Plug-ins

(or the shortcut URL of opera:plugins )

If you see multiple locations of the Shockwave flash enabled then disable all except one e.g. leave the one located at,  /usr/lib/mozilla/plugins/libflashplayer.so enabled.

Restart Opera and hopefully this may clear your problem.