unused level shifter inputs should not be left floating.

[skot]

From the SN74AVC4T774 datasheet

Since this device has CMOS inputs, it is very important to not allow them to float. If the inputs are not driven to either a high VCC state, or a low-GND state, an undesirable larger than expected ICC current may result. Since the input voltage settlement is governed by many factors (for example, capacitance, board-layout, package inductance, surrounding conditions, and so forth), ensuring that they these inputs are kept out of erroneous switching states and tying them to either a high or a low level minimizes the leakage-current.

We need to either connect the input B4 to ground, or tie DIR4 high to make B4 an output.