CRT below limit

This periodic EGM was sent by a Biotronik Lumax 740 HFT with a CRT alert "Biven. pacing below limit (< 85%)". The device was programmed in DDD mode with 5V/0.4ms for LV pacing in bipolar configuration. LV-T wave protection was "on" with a max trigger rate of 120ms. LV sensing was "standard" with a minimal threshold of 1.6mV. What is your diagnosis? What do you advise?

SP