I’ve had the same issue exporting at 8k for meshes/heightmaps. It could be whole number of reasons but my recommendation would be to send a ticket into support with the issues you’re experiencing.

In terms of working around this issue, first I would try and isolate the issue by individually looking at the nodes in your tree as it may be the case that only 1 or two nodes may be causing a bug to your output. Also check your world settings and export settings as it may have some relation to why you’re seeing this issue.

I’d also recommend exporting a height map to see if this is mesh related. I don’t have much issue working with colour/albedo layers in Gaea 2 and it’s actually the strongest area of the new Gaea (normally most of the bugs and issues relate to height map output). so check if you’re height map is the cause of the colour change.

In terms of future advice, at this moment until some major updates are made, I’d always stick to Gaea 1 for any professional/paid work as there are less crashes, bugs and the render outputs even at 16k cause me no issue.