Good to know you fixed the problem!

However... a fuse doesn't burn out without an overcurrent event.
You had the O2S replaced, so the cause might have been abraded wires on the old one, as suggested by Art. In that case you're good.
If they weren't the cause, the actual problem might still be lurking there in the wiring loom.

A couple of years ago, a particular fuse would blow randomly in my 245, even when stationary and ignition off. It took me quite a while to find, and I found it more or less by accident when I moved the wiring loom in the driver's footwell around. A spark showed me exactly where the problem was. A wire had been chafing on the sharp edge of the black sheet metal designed to protect those wires.