The GI relay board is treated like any other controlled solenoid. The circuit is identical to the others in the MPU, there is nothing special about it. Perhaps it was wired incorrectly?

If the driving transistors are blown, you'll find the associated "C" side flashers not working as well. If that is the case, I would also suspect damage further upstream, and start by probing U19s inputs and outputs.

First thing to check would be to make sure there is a diode across the relay coil, and to make sure the polarity is correct. The diode protects upstream components from damage if the circuit is stuck on.

In theory, the GI relay cannot be blown by simply plugging it in. The GI must flash, and that is controlled by the driving transistor, which is controlled by logic upstream. A stuck on driver will blow things like coils and relays downstream from them, not the other way around.