Did you edit /include/staff/ticket-edit.inc.php to update the form?
circa line 71 - 86:
<tr>
<td width="160" class="required">
Ticket Source:
</td>
<td>
<select name="source">
<option value="" selected >— Select Source —</option>
<option value="Phone" <?php echo ($info=='Phone')?'selected="selected"':''; ?>>Phone</option>
<option value="Email" <?php echo ($info=='Email')?'selected="selected"':''; ?>>Email</option>
<option value="Web" <?php echo ($info=='Web')?'selected="selected"':''; ?>>Web</option>
<option value="API" <?php echo ($info=='API')?'selected="selected"':''; ?>>API</option>
<option value="Other" <?php echo ($info=='Other')?'selected="selected"':''; ?>>Other</option>
</select>
<font class="error"><b>*</b> <?php echo $errors; ?></font>
</td>
</tr>