I'm having this problem, too. Is there a solution?
I have a workaround in my scenario. Took me hours to isolate my problem. When I delete from the tracks all FX Chain Presets used, re-save the project, shut down the program, re-open the project, and then re-add the same FX Chain Preset, the problem goes away, and I can export.
Some of the steps above may not be necessary, but this series of steps in fact resolved my issue.