SN74AHCT08Q-Q1: The reaction on used inputs of unused floating pins

Tool/software:

Hi,

I used SN74AHCT08QDRG4Q1 in order to achieve control logic at my board. The board logic normally works as expected.

Therefore, we moved on the mass production phase. However, it is reported that some boards got failed due to MC74HCT14ADTR2G−Q malfunction.

We didn't observe any failure at SN74AHCT08QDRG4Q1. We wanted to ask followings;

There are unused floating pins on SN74AHCT08QDRG4Q1 as shown below. 4pcs of input pins are used, 2pcs of input pins are terminated, 2pcs of input pins are floating.

Here is the configuation:

We only use 1pcs of IC. The all inputs are related to same package.

We don't have any series resistor between ICs and MCU.

1) May this configuration cause any failure on MC74HCT14ADTR2G−Q? What type of failure on MC74HCT14ADTR2G−Q is expected due to this configuration?

2) Can you please evaluate unused floating pin reaction to other operational used inputs?

3) May above unused floating pin configuration cause any high current or oscillation at used inputs that is connected to MC74HCT14ADTR2G−Q?  It is shown as 1 and 2 pins of SN74AHCT08QDRG4Q1.

4) Do you have any critical points that we have to review on mass production for SN74AHCT08QDRG4Q1?

We will also asking relevant question to damaged IC manufacturer.