There are so many, but I will try to list a few.
Mace North America struggles with diversity. There are very few minority employees. You can count on one hand. Mace talks a lot about diversity, but it is not reflective in the workforce.
There have been instances where Mace employees have made racist and culturally insensitive remarks about minority groups in general and specifically to other employees, which management ignores. (See other reviews).
Mace hires people for specific roles requested by the client. When the assignment ends, there is a good possibility you will be without work or assigned to a project you're not interested in. This is because Mace is not proactive, they are reactive, so they wait until your assignment has ended or near ending and then scramble to reallocate you. They will assign you to projects that are not aligned with your skillset and/or career interests just to generate a fee. They are not concerned about your professional growth, only their fee.
Mace North America has a limited client base in comparison to its competitors. As a result, when your assignment ends, you have limited options. They will dangle a carrot and tell you about the many projects they have going on, but for many of these projects, they hire people from the outside to fill and/or they pull resources from a small pool of internal employees they recycle on projects.
Mace North America is top-heavy with men, and again, not much diversity. Boys club mentality.
No employee recognition.
There is a lot of turnover at Mace North America, it's around 20-25% annually. Many people leave due to a lack of promotional opportunities and/or career advancement.
If you decide to work here, get everything in writing. Many broken promises.
Overall, I don't recommend working for Mace. The high score achieved is most likely attributed to positive reviews for Mace UK, not Mace North America.