As an update, both the MG5 and Zoe have been charged several times over the past few days using the Eco mode with no sign of it switching back to 32A charging so I’m assuming it was the Demandshaper causing the issue. I don’t recall doing any configuration or using that module and it seems the OpenEVSE is added automatically when you follow the instructions to generate the feeds.
The only pain is having to remove the timer schedule before it’ll start Eco and then put it back later but hopefully that’ll get changed so the timer only has effect in ‘Normal’ mode.