PulsaCoil Stainless - economy 10 issue

Hi there,

We had a Gledhill PulsaCoil Stainless 150L electric boiler installed in April 2023, before which I had an earlier model of PulsaCoil that developed a leak.

When we had the new one installed the engineers advised that we should go on an economy 10 tariff.
That ended up being a huge confusion with the energy company which said they had put us on economy 10 but eventually admitted we'd been on economy 7 for eight months and moved us over.
The issue with economy 7 has been that while we get plenty of hot water in the morning after the boiler has heated overnight, on the 7 off-peak hours, it runs out in the evening.
My partner works shifts and often needs a shower at about 10-10:30pm, an hour or so before our off-peak kicks in. So we've been relying on the boiler's boost button.

After a few days on the economy 10 tariff we're still having the same issue - that the hot water runs out in the evening. I was hoping that moving to the economy 10 tariff (which gives us 3 off-peak hours during the afternoon as well as 7 overnight) would mean the boiler re-heats itself during those afternoon hours and that would see us through the evening.
I was hoping that we might not be so reliant on the boost (and not have to plan when we have our evening showers), but the problem remains.

Since we've moved to economy 10, I'd noticed noises coming from the boiler within the afternoon hours that suggested it might be heating, but then the light on the off-peak switch (which we always keep on) did not come on as it does during overnight off peak hours. The energy company, despite their previous errors, is absolutely insistant that we're on economy 10 now, so I don't know what to do next.
Do we need to do anything technical with the boiler so it's using the daytime off-peak supply?

We have the boost button plugged into the top immersion, working off the on-peak input, and the off-peak energy supply goes into the bottom immersion.
We only turn the boost button on when we're boosting.

Is there anything obvious that I've missed?

Hi, I had a similar problem and it was solved by swapping the heating element, I hope that helps