To reproduce:
1. Open attached project
2. Look in the project and see that test1 has Letter A and test2 has Letter B.
3. Multi-select test1 and test2 (click one in the project and hold shift and click the other).
4. Notice when you multi-select them, the Letter field flickers and then selects the value from the last selected object.
5. Select the Test objects one at a time and see that they now both have the same values.

Reproducible: 5.5.0b1, 5.4.0p4, 5.3.6p3