According to an Oracle JDBC developer, the problem stems from parsing the Spring JDBC INSERT statement.

https://github.com/spring-projects/spring-framework/blob/612dc573d12d04d8d88ea101f90bc1df9f3e343c/spring-jdbc/src/main/java/org/springframework/jdbc/core/StatementCreatorUtils.java#L274

Spring JDBC calls getParameterMetadata() when setting a parameter to null.
Setting the following property to “true”, prevents Spring from using the ParameterMetadata API:

spring.jdbc.getParameterType.ignore=true

This property can be set either in spring.properties or as a System property.