Finally got it working with PMW+noOneShot at 490. After switching to "PMW+noOneShot" all motors were beeping, but not all at the same time, making it impossible to calibrate. I basically just kept unplugging and plugging it back in until the beeps were close enough together to calibrate the ESC. I'm too scared to try again now that it's working. Still interested in knowing what might cause the other ESCs to beep later than the rest of them. Thanks to all for the help on this!