Is this happening with all LUT files? Can you share the .cube file with us for testing?
You can securely submit your file(s) to our Dropbox using the link below. Please be sure to send me a note to let me know you sent something and include the file name. Submit File to Dropbox
I sent you two luts: Blackmagic 4.6K Film to Video v3.cube, which causes an error during render, and Blackmagic 4.6K Film to Video v4.cube which doesn’t. Strange, but it only seems to be this lut. With the v4 lut I am now seeing the lut applied in the viewer, which is great, but I only see it intermittently, like when I’m using the Fix Focus feature. This is tricky because it’s impossible to compare settings when one has the lut applied and the other doesn’t.