ESA REDUCED

I currently get ESA support group both myself and my partner are claiming PIP. My partner is currently on my ESA claim. My partner's PIP is currently being renewed form sent in on time etc. But with my ESA they have reduced the severe disablement premium that my partner claims on my ESA. DWP are saying because PIP has ended due to it being renewed and there is no new start or end date because they haven't made a new decision on the PIP renewall they cannot pay the severe disablement premium, despite sending the form in on time, PIP has said they will continue to pay my partner's PIP while they are making a decision but there is currently a massive back log. Is this correct as the PIP is being paid that they can actually stop the PREMIUM on my ESA claim many thanks.