Reproduction steps:
1. Open the attached project '_Time'
2. Open the available scene
3. Play scene and observe the material behavior
4. Stop playback
5. Edit the 'Test-wavy' shader
6. Replace line 61 to:

float time = (_Time.w + 10000000)%6.28;

7. Save and play scene

Result: Material Animation in scene jitters when the sin() calculation has huge values in the custom shader

Note: User suggests clamping _Time when it reaches a certain point
Note: Attempting to clamp _Time manually makes no difference

Reproduced with: 5.5.0a2, 5.4.0b23, 5.3.5p5, 5.2.3p3