Mines a c30 plus.
Kept having peculiar things happening to it.
It was under warranty only 2 years old.
I installed.
So I got ideal out turns out the thermisters where dropping in and out between swichnover.
To fast to notice had to be plugged in to show when it dropped out . It was that fast enough to confuse the boiler.
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New thermisters been ok since
Might help
not to expensive to change either
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Mine also played up when running the boys bath.