How to reproduce:
1. Open attached project ("RigidBody MovePosition.zip")
2. Enter Play mode with nothing selected in Hierarchy window
3. Press space to rotate "Player" object
4. Observe the Game View

Expected result: "Player" object can move and rotate at the same time
Actual result: "Player" object stops moving when rotating

Reproducible with: 2017.2.0a4, 2017.2.2p3, 2017.4.1f1, 2018.1.0f1, 2018.2.0a9
Not reproducible with: 5.6.5p3, 2017.1.3p3, 2017.2.0a3

Notes:
Also, MoveRotations stops working when used simultaneously with transform.Rotate

Workarounds:
- If you select a GameObject, in Hierarchy, which has a Collider and Gizmos(Move Tool or Camera icon) then MovePosition works with transform.Rotate.
(MovePosition must be in FixedUpdate and transform.Rotate must be in LateUpdate or Update for the workaround to work)

- If there is ParticleSystem in Scene then MovePosition works with transform.Rotate.
(MovePosition must be in FixedUpdate and transform.Rotate must be in LateUpdate or Update for the workaround to work)