Steps to reproduce:

1. Create a host with longest name possible.
2. Create an item on that host with longest name possible.
3. Open trigger form and for "Expression: field click "Add" and choose the item with long name.
4. Observe that it was added in expression.
5. Enter name and save trigger.

Result: not possible to save
There is an frontend controller error saying that the value is incorrect.
Expected: should be possible to save

Reason is that form is validating the long expression against the DB field length which is 2048, but the expression is actually in a different format in DB.
Same applies to recovery expression as well as trigger prototype form.

Similar cases can result in same error.

1. For example create such trigger in 6.0 and import it. In item list click ". . ." and choose create trigger for the item with long name. As result, the form doesn't open.
2. Import from 6.0 and open the trigger form. It opens. Press "Clone" and again there is the same error.