Anycubic Chiron - Issue in only one place on print

[DBW]

Hello,New on here and looking for some pointers. I have a new Anycubic Chiron which I think is great. Huge build volume and I'm already making some progress on my project. But...I have a particular artefact that I'm trying to resolve. On one specific area on the print I get the issue as per the pics. The rest of the print is excellent quality with no artefacts. I've tried a few different slicing adjustments in Cura but I get the same result in the same area. Does this look like the temp is too high/low or print speed or cooling issue? I'm not sure what to adjust next and don't want to just tweak at random. The settings are a large nozzle at 1mm and no infill as I need to fill the print with foam when done. I've tried various layer heights. Any advice very gratefully received. IMG20201202200739.jpgIMG20201202200835.jpgissue3.jpg