Removing defects from an execution does not update the "Test Execution Defects" custom field

Removing defects from an execution does not update the "Test Execution Defects" custom field.
How to reproduce:

• create Test Execution with a manual Test
• create a defect from the overall test run (top of execution screen)
• create a defect from one step
• list the Test Execution in order to see the "Test Execution Defects" custom field
• go to the details of the execution of the manual test
• remove the defect from the overall defects and from the one that is linked with the test step
• list the Test Execution in order to see the "Test Execution Defects" custom field; this is still 2 and should be 0 (it is not being updated)