ResourceBundleMessageSource properties not working

Question

So, I was using JDK 8 with Sprint Boot 2.0.3 before and now I moved to JDK 11 and Spring Boot 2.1.1. And I had the TemplateEngine Bean which processed the thymeleaf templates for the email and it was working fine with the below configuration of ReloadableResourceBundleMessageSource

ReloadableResourceBundleMessageSource messageSourceThymeleafConfiguration = new ReloadableResourceBundleMessageSource();
messageSourceThymeleafConfiguration.setBasename("classpath*:i18n/messages");
messageSourceThymeleafConfiguration.setDefaultEncoding("UTF-8");

And now that I have moved to JDK 11 and Spring Boot 2.1.1 it has stopped working all of a sudden and in the emails instead of the locale based translations from the properties file the property keys are being displayed. For example:

??email.greeting_en??
??email.text1_en??

I even tried to replace the ReloadableResourceBundleMessageSource bean with ResourceBundleMessageSource and try it and it still doesn't work. I tried to meddle with the base name string by using classpath:i18n/messages, i18n/messages still doesn't seem to work.

Any help would be highly appreciated.

Edit: This is how my entire Configuration related to this looks

@Configuration
public class MailServiceThymeleafConfiguration {

    @Bean
    public TemplateEngine templateEngineThymeleafConfiguration() {
        SpringTemplateEngine templateEngineThymeleafConfiguration = new SpringTemplateEngine();
        templateEngineThymeleafConfiguration.setTemplateResolver(emailTemplateResolver());
        templateEngineThymeleafConfiguration.setMessageSource(messageSourceThymeleafConfiguration());
        return templateEngineThymeleafConfiguration;
    }

    @Bean
    @Description("Thymeleaf template resolver serving HTML 5 emails")
    public ClassLoaderTemplateResolver emailTemplateResolver() {
        ClassLoaderTemplateResolver emailTemplateResolver = new ClassLoaderTemplateResolver();
        emailTemplateResolver.setPrefix("mails/");
        emailTemplateResolver.setSuffix(".html");
        emailTemplateResolver.setTemplateMode("HTML5");
        emailTemplateResolver.setCharacterEncoding("UTF-8");
        emailTemplateResolver.setOrder(1);
        return emailTemplateResolver;
    }

    @Bean
    public MessageSource messageSourceThymeleafConfiguration() {
        ReloadableResourceBundleMessageSource messageSourceThymeleafConfiguration = new ReloadableResourceBundleMessageSource();
        messageSourceThymeleafConfiguration.setBasename("classpath*:i18n/messages");
        messageSourceThymeleafConfiguration.setDefaultEncoding("UTF-8");
        return messageSourceThymeleafConfiguration;
    }
}