Unity hangs while importing Blender generated PNGs

Sometimes Unity “hangs” (import taking what looks like forever) while importing PNGs created with Blender.
Upon restarting Unity I then have to manually force re-importing the texture, which then happens without error.

Not a big problem except that, since importing can take a while, I sometimes end up waiting for imports that will never complete.

Any input on this much appreciated.

It sounds like a bug. You should submit it with your file.