The Kahanga palace rooftop map has letterbox bars cutting the background on left and right. Gameplay is unaffected but it looks pretty bad, screenshot here.
That's 3440x1440.
I'm getting the same error. Kinda hard to attach stuff with a 507kb forum size limit so my save is at:
https://1drv.ms/u/s!Aono4wQErK9xg6c_xDDfiRjv4gZJ9w