After several tests, we could reproduce and isolate this issue.
It happens because in Corona the Max interface is not locked while rendering. You can select objects, modify them and more.
In this case, if you move the cursor over a FP object, that may trigger a "pick" action and rebuild the object. That invalidates some data which is stored in Forest Color/Edge, which assumes that the object is not modified once that render is initialized.
This is a hidden problem which has arised now, because in the latest releases we added a security mechanism to Forest Color/Edge, to provide compatibility with Interactive Render.
Because its nature, in Interactive Render it's normal than FP objects change while they are rendered (because the user interaction). Previously, that would cause a crash... now just Forest Color/Edge is not applied temporary.
I just wrote to the Corona team to discuss about this issue. Meanwhile, you can go back to FP 5.3.0, or just avoid to move the cursor over the viewport while rendering.
Apologies for any inconvenience.