I experience this strange behaviour since one of the 18.12 releases (not sure when it started; I have worked with 12.1, 12.3 and now 12.5):
The very first drag & drop action in a MC editing session (clips to bin, effect to clip, etc.) takes an abnormally long time to complete; e.g. when I drag an effect and drop it on a clip, nothing happens, the mouse pointer doesn't change and the effect is not applied; the second attempt works, and any other drag-drop action after that is just fine .
It looks much like this: http://community.avid.com/forums/p/185073/860592.aspx#860592 but I'm on PC and no BTT here...
No clue...anyone else seeing this ?