SOLVED - Houdini Mantra Render error: Failed reading scanline in file "xxxx"

I know its not shotgun related (since we have tried with the shotgun mantra and normal mantra) but has anyone ever seen this mantra render error?

Failed reading scanline in file “G:/Projects/project/shots/shot_010/lighting/publish/houdini/output/ENVIRONMENT_L010_BEAUTY_v002/images/1920x1080/ENVIRONMENT_L010_BEAUTY_v002.1012.exr (line 1023) : File exists”.

It’s failing on each frame with this message (the error is reported for all lines in the exr)

For anyone searching for the answer.

Mantra runs a postprocess on exr’s if this is enabled.
For some reason in Houdini 17.0.459 the postprocess to render a DWAA or DWAB exr seems broken.
Turning it off or on doesnt make a difference and a bug was logged with sidefx.