Please follow the below steps on USMF Legal entity on a Contoso environment. The environment version that I have used is :

Installed product version : 10.0.24 (10.0.1084.80)

Installed platform version : Update48 (7.0.6253.76)

Pre-requisite: 

1. Navigate to Organization administration > Setup > Cases > Case processes

2. Create a case process, Ex. "TestProcess". 

3. Click on Action menu "Process > View > Details".

4. Create activites of type "Task" and mark them as "Required" (See figure 1 in the attached document).

5. Navigate to Organization administration > Setup > Cases > Case caegories

6. Take any case cateogry (ex. ServReq) and select the above case process "Testprocess" on the field "Case process" on the case category (See figure 2 in the attached document)

Steps:

1. Navigate to Common > Cases > All cases

2. Create a case with case category. Select Name = 000002630 (Contoso Entertainment System USA). Click on "Select"

3. Select a case category from the "Tree view" : Case category > Service > ServReq

4. Click on 'Create' 

5. Verify that the 'Case process' field is populated with value 'TestProcess'.

6. Click on the action menu "General > Activities > View activities. The activities associated to case process are visible.

7. Click on any activity number. 

Actual Result : The 'Description' field on the 'Activity' form does not show any existing text. User cannot write new text on it (Figure 3 on the attached document)

Expected Result: The 'Description' field on the 'Activity' form should be editable and users should be able to write / read from it.