I've never noticed this before, and I'm fairly sure that's because it hasn't happened before, but I could be wrong.
 
I have an audio track with reverb on it. The clip in question is the very end of the song. I realized I needed that last audio clip to be shorter, so I dragged the right edge in to shorten it. However, now the reverb on the track abruptly stops right at the end of this truncated clip.
 
Without success, I have tried:
1. Adding a volume envelope and reducing volume to zero rather than shortening the clip
1. Recording a clip of silence and adding that to the end of the track
2. Reducing the actual gain of the end of te clip itself to zero (rather than using an envelope)
 
All these methods caused the reverb to stop when the clip stopped. If it's important, the effect is part of an FX Chain Preset I loaded.

In preferences there is a setting for always stream audio through fx or some such thing.
Tick that and you should be golden.

Not sure if there's a fix for X3 but in the latest versions there's a preference for "Clip Tail Duration." Prior to that, I just extended the clip for however much reverb or delay I wanted.

There used to be also "Play FX tails after stop", I don't know if it's there anymore under that title. Maybe it's now the same as Bitman refers to.

Possible solution/workaround.
 

1. Drag the clip containing the reverb out for as long as the reverb tail extends
2. Automate the track volume for the length of the extension down to -INF

Once the reverb tail may vary, I always stretch the last clip for a time sufficient to keep the full tail.

It seems like the OP has a clip that sounds too long and wants to shorten the clip and have the reverb continue. But shortening the clip also shortens the reverb. Dragging out the clip results in the too-long note/chord.
 
jko, I would split the clip, delete the end, save, close, re-open then drag out the truncated clip.
There are probably better ways to do it.

57Gregy
It seems like the OP has a clip that sounds too long and wants to shorten the clip and have the reverb continue. But shortening the clip also shortens the reverb. Dragging out the clip results in the too-long note/chord.
 
jko, I would split the clip, delete the end, save, close, re-open then drag out the truncated clip.
There are probably better ways to do it.

This is exactly why I said automate the track envelope of the bit with the tail that he doesn't want to hear

57Gregy
jko, I would split the clip, delete the end, save, close, re-open then drag out the truncated clip.
 

Exactly. Three easy steps:
1. Shorten the clip with a slip-edit 
2. Bounce it
3. Stretch the new clip as far as needed to keep the reverb tail going

Bit, you forgot the "There are probably better ways to do it."
Thanks, I can use that.