Mmm I do not know ... how?
Troester is correct, and you problem is in using a non-unique key for Localidad. If I unpublish that element, the list loads in a couple of seconds.
Your "
Localidad" join isn't using the 'id' as the join's value from the gestion table, it's using the "localidad" field. And that isn't unique. For instance, you have 12 rows in that table with "Firmat - 2630" as the localidad. So when any row on your institucional table tries to use "Firmat - 2630" as the key to join the right row from gestion, it winds up joining 12 rows. So on the first page of your main table, where you have 5 rows joining to those 12 rows ... that means 60 rows are being selected rather than 5, just for those first five, and Fabrik is having to then narrow that down to just the "distinct" ones. That whole page of results is problems trying to load up to 1000 rows or so.
The "key" that you select for a join MUST be unique, and should pretty much always be the one we put "recommended" next to, usually 'id', which is the PK (Primary Key) of that table. The whole point of PKs in database tables is to provide a unique id to reference that row with for join relationships.
So you'll have to repair your data. Your first problem is that everywhere you have select a Localidad using a name that isn't unique in the gestion table, you'll have to figure out which of the multiple rows it was supposed to join to. And you next problem is actually changing the data.
You can't just change the key in your existing join, because that will blow away all your existing data, which is stored as the "localidad", not the P (id) value.
So ... your first step would be to create a new element on the main table, called something like Localidad_new. Make it a join to the same table, only this time select 'id' as the key.
Then you need to decide if you want to go through and manually edit every row in the Institutional list and set the new element by hand, or whether you want to try and do it with a query by hand in phpMyAdmin. Which wouldn't allow you to choose which of the multiple matches to set them to, but you could (in one query) set the "new" element to be (say) the first match for a given name.
Once the "new" element is set with the ids, you'll be able to use phpMyAdmin to rename the original on to Localidad_old (or whatever), and rename the new one to just Localidad, and change the key in the original element in Fabrik.
This is way outside the scope of "standard" support, so if you need much help on repairing this, it may have to be billable work.
-- hugh