Is there a reason that I don't see this question in the forum? Most forums show the most recent posts at the top. This one has "Trending Questions", and this is not in the list.
Is an Adobe employee monitoring this forum? If so, do you have access to a list of known bugs? Is this on it?
This is a user to user forum with, as far as I can remember, very little or no postings by Adobe employees
You may file a bug report at https://www.adobe.com/cfusion/mmform/index.cfm?name=wishform
Otherwise, more information as asked for in http://forums.adobe.com/message/4200840 might help (different product, but information needed is the same)
Also, information on what you are editing may help
Read Bill Hunt on a file type as WRAPPER http://forums.adobe.com/thread/440037
What is a CODEC... a Primer http://forums.adobe.com/thread/546811
What CODEC is INSIDE that file? http://forums.adobe.com/thread/440037
Report back with the codec details of your file, use the programs below... a screen
I personally find that Keyframes, and especially when used with the Fixed Effects, like Opacity, Motion>Position, Motion>Scale and Motion>Rotation, are mose easily done from the Effects Control Panel, rather than via the "rubberbands" in the Clip. To access the Effects Control Panel, just Select the desired Clip, then from the Effects Tab, choose Edit Effects. There, if you have added, say Opacity Keyframes, you would just advance to the first Keyframe, that you wish to adjust (there is a Next/Previous Keyframe button, that is very handy for this, for each Effect, that you have added Keyframes), and then make the adjustment to that Effect's parameter, at that Keyframe. To make another adjustment, just proceed to the Next Keyframe, and adjust the parameter there.
Some users DO like using the rubberbands, but I find those fiddley, and as one has to toggle through all of the Fixed, or added Effects, to get to them, for each Clip, prefer to see it all, in the Effects Control Panel. If you do not see the Effects Control Panel's "mini-Timeline," go to the double arrow icon in the Effects Control Panel, to reveal that mini-Timeline.