When compressing textures with 'ETC' or 'ETC2' methods, Unity hangs.

Steps to reproduce:
1) Open the latest attached project (ImportTest.tar.gz).
2) In Build Settings > Android > Texture Compression, select 'ETC' or 'ETC2'.
3) Click 'Switch Platform'.

Unity hangs. Selecting other compression methods prevents the issue (if 'Don't Override is selected, 'ETC' is set by default and issue still reproduces). This does not occur when switching to other platforms (due to different compression methods). Often the whole system hangs, requiring a manual reset. This happens with all textures.

Reproduced on:
5.6.0b3, 5.5.0p1

Did not reproduce:
5.4.0f1