A problem with the ML555 SFP TX Disable circuit has been identified. The SFP/MSA specification states that all SFP modules have an internal 4.7K PullUp on the SFP TX Disable pin. The ML555 has a PullDown on the SFP TX Disable pin external to the SFP module. Since there is already a 4.7K PullUp inside the SFP and a 4.7K PullDown external to the SFP TX Disable pin, this can cause the TX_DISABLE pin to go to an "undefined" logic state.
As a work-around, replace R402 and R394 with 1K ohm resistor.