Repro steps:
1) Open the project and GameScene.scene
2) Play the scene
3) Press Space - notice gravityScale in Player's Rigidbody2D becomes 0
4) Press Esc - notice the position resets, gravityScale = 0.5 and the object falls again
5) Open PlayerController Script and swap lines 31 with 32
6) Repeat steps 2 to 4 - notice that position resets, gravityScale = 0.5 but the object doesn't fall and the gravity affect the object

Reproduced in: 5.4.0b2; 5.3.1p3; 5.2.3p3