As per the information given in the question, the departments stated that due to the setting up of a target goal too high, employees are missing their personal target across the board.
The motivational theory that I think is best for describing human behavior in the workplace as per the information given in the question is the "Two-Factor" theory. The two-factor theory assists in defining and identifying the factors that will either motivate individuals in the workplace or dissatisfy them.

Step-by-step explanation

In 1959, a behavioral psychologist, Frederick Herzberg, suggested a two-factor theory or the theory of motivator-hygiene. There are a few job factors that lead to satisfaction as per Herzberg, and there are other work factors that prevent dissatisfaction. The Motivation Theory model of Herzberg, or Two Factor Theory, claims that there are 2 factors that could be changed by a company to affect workplace motivation. These factors are as follows:
a. Motivators: They can inspire workers to work harder. "Factors of motivation, or intrinsic motivators, usually reflect less concrete, more emotional requirements, that is, the sort of needs defined in the needs classes" relatedness "and" development". Intrinsic motivators include tough work, appreciation, relationships, and potential for development. Managers need to understand that while these criteria can fall beyond the more conventional scope as to what a workplace must offer, good individual and team success can be crucial.
b. Hygiene factors: Hygiene or extrinsic motivators appear to reflect more tangible, fundamental needs. Status, job security, compensation, and fringe benefits provide extrinsic motivators. For managers, it is necessary to remember that not having the required and anticipated extrinsic motivators can sow frustration and decrease employee morale. These will not inspire workers to work hard, and if they are not present, they might cause them to be unmotivated.
The model of acquired needs indicates that a transition is often encountered through contact with the environment and influences job efficiency in the same way.
Given the condition, as per the question above, of the workplace, the employees would be motivated by giving them an opportunity to complete the tasks early on. Necessary improvements in services, such as easy access to coffee, tea, or other canteen food, would allow staff to encounter a new situation by bringing food to the desk through a supplier.
Employees shall be given the option of extending their lunchtime by half an hour and then also of extending the working time by half an hour if employees have chosen the former.
This will provide the ability for employees to use their time in a flexible manner. Weekend celebrations are scheduled and a holiday at the end of the month is awarded to the best performers including tickets to films or other locations, and more.
Top performers shall be drafted into one pool, and the majority of the contestants shall be drafted into another pool, and competitions shall be given separately to each. This will allow staff to compete with people of the same level and many similarities between the results of the two pools will be found in due course of time.
Through the job, incentives, the staff would be inspired to succeed. Since the incentives provide something that can strengthen their family care in the form of monetary support, family time, and more, employees will have a passion for building their lives at home and at the workplace. The creation of lives for a shared good cause at homes and at the workplace would help to achieve employee satisfaction.
Reference:
http://www.whatishumanresource.com/herzberg-two-factor-theory
https://expertprogrammanagement.com/2018/04/herzbergs-two-factor-theory/
https://courses.lumenlearning.com/wm-organizationalbehavior/chapter/herzbergs-two-factor-theory/