The problem of counter intuitive signs in MMM

In MMM, sometimes we come across situations where we find that the signs of certain variables are counter intuitive. For example, the media spend variables should have a positive coefficient as it is believed that media spends impacts the KPI positively. Similarly, the coefficient sign for price variables should be negative as it is believed that an increase in price decreases the KPI under study. So, it is crucial to get the correct coefficient signs for the variables in the model.