THREE.WebGLProgram: shader error:

I just updated from 116 to 120 and all is (most is) working fine. Fixed a few problems I had with Reflector.js and others, but today noticed that when I turn on shadows on lights
light.castShadow = true;
I get the following error
THREE.WebGLProgram: shader error:
and I get 1 error and about 200 warnings
WebGL: INVALID_OPERATION: useProgram: program not valid
ERROR :GL_INVALID_OPERATION : glDrawArrays: Source and destination textures of the draw are the same.

And I get no shadows.
If I comment that line out then I get no error or warnings

Any ideas?
I have the examples from 120 and they seem fine, not sure what could error from just 1 line.

Please demonstrate the issue with a live example: Edit fiddle - JSFiddle - Code Playground