Can you override (/ "solve") that using a scheduler such as TeslaFi?
My car is often charging during the day, from PV, and the AMPs gets adjusted according to what spare PV is available (not much this time of year!) and, consequently, sometimes the car is "confused" when Off Peak starts. So I have TeslaFi (in my case) set to CHANGE AMPS to 32 (could be 28 in your case) just before the start of Off Peak. But it could be scheduled repeatedly, at intervals, throughout the Off Peak period, then if the AMPs drops (e.g. because it senses low Voltage, because other stuff has come on during Off Peak), and if the car fails to readjust back up - then a recurring . my schedule could "push" that request
All these bits-and-bobs just to save me from waking up to a half-charged car - because e.g. I lowered the AMPs for some reason, yesterday, and forgot to put them back up
I don't use the in car schedule. It's far easier than faffing about with complicated ways of making it do what I want. I don't do enough miles to need an off peak tariff so it doesn't matter when the car actually charges, just that it does.