Steps to reproduce:

1. Open attached project
2. Open scene "TestScene"
3. Build asset bundle using "Assets/Build AssetBundles" menu
4. Run scene and notice message in console that bundle was downloaded successfully
5. Exit play mode
6. Open "_Game/Textures/test1.bmp" using paint and edit it a little
7. Build bundle again and run scene
8. Notice errors:
"Error while downloading Asset Bundle: CRC Mismatch. Provided 7b124d9a, calculated ab4aa80b from data. Will not load AssetBundle"
"UnityWebRequest Error : Unable to write data"

Note: not reproducible using WWW

Reproduced with: 5.3.6p7, 5.4.2f1, 5.5.0b7