I do not get anything with a print_r on a new template using a test post. But it is definitely the correct ID (with prefix included) and there is definitely a value in the test post to output. No error messages when trying to get the value.
But I use elementor as my page builder, with the elementor dynamic conditions tool, I can successfully output the test post value. Does that use the rwmb_meta() ?
I also checked in my code with a wp_mail(...sprintf()) and all the other fields had a value except this one and another number field where the value was also an integer.
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with the details of the issue. I will take a closer look.