I don't know if this really faces your problem but since an update of some database connection implementations in QlikCloud there are some limitations when there is ne need to extract more than 255 characters from Db table columns.
AFAIK there are currently to workarounds to deal with that:
No. 1) https://community.qlik.com/t5/App-Development/DATABASE-LOAD-CHANGES-LENGTH-WHEN-SWITCHING-TO-MEMORY-...
Which uses the SQL "CAST" command to tell QlikCloud to handle the db table column as if it where of another type, i.e.
CAST("columname" as CHARACTER VARYING(16384)),
BUT: From what we know, this works only up to 16384 characters and i.e. TEXT fields which can carry unlimited characters will still be extracted with max. 16384 chars and the any char beyond is not being extracted.
The following No. 2 works stable and robust:
No. 2) Add this advanced parameter when creating an DB connection in QlikCloud:
Using this parameter will allow you to extract all content from db fields, even from Postgres TEXT fields.
Hope that helps.