How to reproduce:
1. Open the attached "1233899 repro" project
2. Open the "SampleScene" Scene from the Assets/Scenes folder
3. Select the "Cube" GameObject from the Hierarchy window
4. Press the "Test" button in the Inspector window under "MyScript" Script component
5. Repeat the 4th step without moving the mouse in between the steps

Expected result: it is possible to click the button multiple times without moving the mouse as shown in "ExpectedResult.mp4"
Actual result: the button gets stuck if the mouse isn't moved in between clicks as shown in "ActualResult.mp4"

Reproducible with: 2019.3.0f3, 2019.3.9f1
Not reproducible with: 2017.4.39f1, 2018.4.21f1, 2019.3.0f2, 2020.1.0b5, 2020.2.0a7

Notes:
-This bug does not reproduce if "DisplayProgressBar" is used instead of "DisplayCancelableProgressBar"
-Sometimes the 5th step needs to be repeated a couple of times before the button gets stuck
-Succesful clicks are indicated by the Debug.Log "Test" messages