Shift Register Port Expander, lsrio16 comp

I have built a small control panel for my small "cheesemill" , it hangs on a second parallel port. To have enough inputs I connected the small TSHW parport board from talla83 and intigrated the lsrio component in the Hal.
github.com/talla83/tshw-parport

There are two 74hct597d soldered on the board.

unfortunately not all inputs work reliably.

Some buttons always work, some only intermittently,
the faulty inputs are distributed on both 74hct597d.

the board looks clean soldered.
I rewrote the configuration and connected the panel to the other parallel port, but it didn't change anything.

what else can it be?

panel and parallel port cable are shielded!
could it be a latency problem?


Grüße
Werner

no i have no latency warnings,

yes there are 2 small caps near to the chips.
i will check the values.

Perhaps the PCB is still too dirty with flux that creepage currents occur?


If it looks like a hardware problem, I should still have all the components to assemble a second board.

hm
i think the t in hct597d  stands for ttl

i have 2 74hct597d on the board witch makes the troubble.
if i remember right i have also 2 74hct597t at home, but i was not able to google the difference

unfortunately i do not have a ttl tester
easily DIY? äähm how?

the caps on the board have a capacity of 100nF

as chip at the moment i have 2 74HCT597D on the board.
i have also some pc74hct597t which I also ordered at that time

should I exchange the chips for others?