Stange VIEW problem

I'm using Firebird 1.0.3 and have a VERY strange problem with some VIEWS in the database.

The problem started suddenly after a time in which everything worked fine.
The problem appears when something has to be fetched from the view (for example DIST_TL_PickID).
I get the following error:
"Arithmetic exception, numeric overflow, or string truncation"

First I supposed that there was a problem in the data in the tables that the view referenced but when I emptied all of them and added a single line in one the problem stayed.
Then I tried backing up the data and restoring - again error

Then I recreated the view and everything was OK.

That is fine but the problem kept showing up randomly so my question is if there is someone that can help me prevent it and explain to me how it happens?


I've attached a small database showing the problem