Can one circuit trip a GFCI breaker on another circuit with no shared neutral

I have two circuits in my main breaker panel.

Circuit 1 is on a 2 pole 60amp GFCI breaker. It goes directly outside from the breaker box and does not interact with the house aside from at the main breaker box.

Circuit 2 is a single pole 20amp breaker that feeds lights in the garage.

Some times (not all the time) when I flip a switch to turn on the garage lights (circuit 2), the GFCI breaker on circuit 1 trips.

I have opened all of the light cans and switch box on circuit 2 and everything seems wired correctly.

I have tested all wires on circuit 1 for shorts to ground and shorts between wires. All tested fine.

There is no possibility of the two circuits sharing a neutral on the load side.

How can this be?