Jerking happens when the parent div ".collapse" has padding.
Padding goes on the child div, not the parent. jQuery is animating the height, not the padding.
Example:
<div class="form-group">
<a for="collapseOne" data-toggle="collapse" href="#collapseOne" aria-expanded="true" aria-controls="collapseOne">+ addInfo</a>
<div class="collapse" id="collapseOne" style="padding: 0;">
<textarea class="form-control" rows="4" style="padding: 20px;"></textarea>
</div>
</div>
<div class="form-group">
<a for="collapseTwo" data-toggle="collapse" href="#collapseTwo" aria-expanded="true" aria-controls="collapseOne">+ subtitle</a>
<input type="text" class="form-control collapse" id="collapseTwo">
</div>
Hope this helps.