For now, and following ur comment in other topic, i have disabled coupon queueing:
“I suspect the ‘coupon queueing’ feature conflicts with the checkout plugin. If you don’t need this functionality you can disable it from the settings page. You need to temporarily enable debug mode. After disabling coupon_queueing you can disable debug mode and it’s functionality will stay disabled.
The coupon_queueing allows deferring application of a coupon until it’s restrictions are met.”
Disabling this make the remove coupon functionality works well.
But u should take a look on that coupon queueing, as it seems it is not working well under various circunstances.