Steps to reproduce:

1. Open attached project
2. Open scene "repro1"
3. Select "Particle System" in hierarchy to start simulation
4. Once particles are emitted - pause simulation
5. Expand shape module and change Angle value from low one to higher one
6. Notice that particles get their rotation reset to 0 once low Angle is set

Reproduced with: 5.5.0f1, 5.5.0p3, 5.6.0b2
Not reproducible: 5.3.7p2, 5.4.4f1