I'm using the I3 in a non-Cloud Home-Assistant setup. The issue though is also visible in the I3's UI.
Voltage used is 25v DC. The inputs are switch using AC-Relays. Inputs are set as Momentary.
After a reboot of the I3, the inputs work as designed. Doing a 2nd switch after a few seconds is then not recognized.
Interestingly enough, after rebooting, the settings of the inputs are correct!
I tried using FW 20201124-092930/v1.9.0@57ac4ad8 and beta FW 20201202-141633/v1.9.3-rc3@50c6ab57 but both have the same issue.
It seems as if it is reacting only every second change.