Fixed for the next 19.1 beta build.

All DataFlex SQL Drivers:
Passing a variable length parameter (e.g varchar(max) ) for a stored procedure with SQLSetParameter could in some circumstances cause an exception.

When receiving result messages from a stored procedure or SQL script with SQLGetMessage, messages would be limited to 512 characters. The maximum length for result messages has been increased to 1024.
Clive already tested and confirmed the fix.