Matinee crashes on Movie Capture

When I try to Capture Movie (png Image Sequence) in Matinee in UE 4.11.2 the program either quits or freezes.

When I open the same file in UE 4.12 Preview 2 I have no problems writing out a png sequence from Matinee.

(I can’t just stay with 4.12 as I use “Water Planes” in my scene – which is incompatible with 4.12)

I’ve read the other related posts and they don’t help

Any ideas gratefully received.

Thanks