The clock cap on the xboxes are constantly dying/leaking. They arent needed on a modded xbox though. so we generaly just remove them.
they only really cause issues on stock xboxes as some bright spark decided that the clock needs to be set properly.
This isnt a big issue though just means you have to reset the clock when you power on, but a dashboard error + dead cap throws up a diferent error to just a bad dash, and then you have to hotswap to fix where as otherwize you could have gotten away with a live enabled game dash update.
you can replace them with a battery, but generaly we dont as the charging part for the battery is not properly regulated as the xbox is expecting a cap not a battery.
you can just prevent power getting to the battery by using a diode or similar but a battery that wont be charged is not really any more usefull than a dead cap IMO.