Hello Hanna @Hcube7,
You are right, the number bit reset needs 5 Volt on the SIG connection to reset.
When you have an older version of the button bit, it will only connect it's input SIG connection to it's output SIG connection, so there will be no 5 Volt on the reset.
When you connect a power bit to the button bit, the input SIG is connected to 5 Volt from this power bit, so now you can reset the number bit by pressing the button.
So it is supposed to happen as you discovered.... 😊