With a rule like this: (See, a semicolon is missing in the "p2.age = 30" line)

rule R
dialect "mvel"
when
  Person(name == "Mario")
then
  Person p2 = new Person("John");
  p2.age = 30
  insert(p2);
end

exec-model fails with

CompilationProblemErrorResult: org.drools.mvelcompiler.MvelCompilerException: RHS doesn't have a type

while standard-drl runs successfully.

I'm not sure if exec-model should work the same as standard-drl (treat a new line as a delimiter?), or give a better error message.

This looks to be a rare issue but when using spreadsheet, it's possible to forget to add a semicolon. (Then users don't notice the mistake because standard-drl executes it succesfully)