P: Crash hangs indefinitely mixer brush

Photoshop 2015.5: in 2 of my machines photoshop appears to hang idefinitely using mixer brush on a 16bit document with the latest version: 

steps:

create new document: file->new ->ok

change mode to 16bit image->mode->16bit/channel

select mixer brush, alt click to sample the background of the new document (or just sample something), then make a stroke in the document.

create another document: file->new->ok

 

photoshop hangs indefinitely.

 

also happens if you have the second document already open and you switch to it with the mixer brush active (instead of the last step of creating a new document)

 

another similar way to crash photoshop:

 

create new document

select mixer brush, sample the background and make a stroke in the document

change mode to 16 bit image

photoshop hangs.