SQL statements/queries with a percent sign in a string are not transformed correctly. In most cases, parameters (starting with a colon) will not be detected (or the statement will just not retrieve any results).
SELECT Name, Population FROM Country WHERE Continent LIKE '%:Continent%'
SELECT * IN x WHERE x.y = '%:xparam%'
This has been a long-lived problem that is technically not easy to fix. The workaround is to use a string concatenation function available in your SQL dialect. In the case of MySQL, for example, the above examples will work like this:
SELECT Name, Population FROM Country WHERE Continent LIKE CONCAT('%', :Continent, '%')
SELECT * IN x WHERE x.y = CONCAT('%', :xparam, '%')
Another workaround that might work for your use-case would be to use the parameter type `Constant` for your parameter (see "Parameter Types" section in Queries manual).