Surely if its sinking it's a leak. I knew mine was not leaking as with the sls inac warning up the compressor is disabled so after a week with the light on it did not lower. Yours I would say is leaking on that front corner and I'm pretty sure the valve block has feed for front and back and accumulator so if accumulator is empty it diverts air straight to bags then tops off accumulator after

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2005 X5 4.8is - 1995 Discovery 300tdi - 1970 Series IIa - 2004 CCM 644DS -2000 ZX12r