For Shelly 1 and Shelly 2.5 there is no need to rollback the firmware.
The IO/URL actions are webhooks, instead of rolling back the firmware simply manually update these webhooks.
Hubitat uses the following patterns for the webhooks:
http://ip_address:39501/device_type/switch_id/action
ip_address: IP for your hubitat
39501: port used by my hubitat for these callbacks. I am guessing it's the same for everyone, but if it does not work check the URL Actions for a working switch to confirm.
device_type: either "button" or "switch"
switch_id: always 0 for Shelly 1, but maps to the switch number for Shelly 2.5 (0 or 1)
action: see below
On your Shelly 1 built-in URL Actions screen:
Button Switched On URL
Left blank
Button Switched Off URL
http://[ip_address]:39501/button/0/released/
Button Long Press URL
http://[ip_address]:39501/button/0/held/
Button Short Pressed URL
http://[ip_address]:39501/button/0/pushed/
Output Switched On URL
http://[ip_address]:39501/switch/0/on/
Output Switched Off URL
http://[ip_address]:39501/switch/0/off/
For Shelly 2.5 you enter the above for "Switch 0" and then change all the zeros for ones when entering "Switch 1" actions.
The button long and short press actions are only for momentary switches.
If you have toggle switches then these two actions are not needed.
Don't forget to check the "Enabled" box, and click "Save" for each individual action.
I tested on Shelly 1 and Shelly 2.5 devices. Everything worked as expected.
Hopefully Hubitat fixes this in a future update.
