To understand a parking brake that does not hold, compare it under normal, safe conditions: cold versus warm, idle versus steady speed, and light versus higher load. Record the slope and whether the lever or switch feels different. Change one condition at a time so the result stays useful.
Do not create a risky test just to reproduce it. Use the parking brake only as directed; park on level ground and use the transmission position as a backup.
Quick educational note
For information, not a diagnosis or repair instruction. Vehicle-specific checks are still required. Consult the manufacturer's guidance and a qualified technician.
How to use this information
This article explains general principles and does not establish what is wrong with your vehicle. Read the content limitations.