It could be the potentia coil has suffered damage to its power generation or its fastening to the cyber mantle, therefore draining the techmarine of his much needed energy to recover properly.
Since normally the augments would be powered by the potentia coil, if it is damaged it could be that the implants are draining energy from his usual metabolic system as a failsafe to keep him from dying. For example if his respiratory system is bionic and it looses power from the coil he wouldn't be able to breathe unless there was a failsafe.
A battery is probably the standard system, but that battery might have run out so it is now tapping into other systems to work.

I am just considering reasons why the mechanicum implants might be acting up.
Also, being what he is, Zuriel will be able to fix a lot of that. Not because he is a mech wright, but because he has been given vast knowledge of technology from the Liber mechanica.

As the character sheet doesn't specify which other bionics he has apart from the standard mechanicum implants (Cyber mantle, potentia coil, electoo inductors, cranial circuitry, voice modulator and respiratory filter, electro-graft)

I cannot say anything for sure since that information is held only by Wraithblade6 at the moment.

(Also i'm a bit sad, i forgot 1,5 implants, otherwise i would know them all by heart :P )