Why is my electric bike 'clanking' under load?
That crank is unusual and therefore it is hard to give you advice.

It shouldn't be the bearings because they don't usually make a big noise, but
rather make the crank harder to move around (you can perfectly feel bad bearings if you try moving it with your hand and feel resistance/side-to-side movement).

Can you install the crank without the clutch mechanism, or simply install another crank, and test if the noise goes away? My bet is it will :)

If the noise goes away, the best is to contact Giant support or a representative and see what they can do for you (send you new pieces, help troubleshooting, etc). If they can't do anything for you, at least ask them to advise on a solution, or to suggest a list of cranks that are compatible with the electric system, in case a normal crank does not work.

While testing keep in mind this can be a malfunction piece which might fail to perform at the worst possible moment, so take it easy. Good luck.