great find and good attention to detail! it even makes more sense because both bond0 and bond1 are in the same subnet so a [jumbo] frame could be sent from bond1 on san01 and be received by bond0 on san02. And because the default frame size for ping is 1500 mtu, that makes it seem like connectivity is good!
i'm going to make those changes and see if they fix it. i'm pretty confident at this point!