As suggested by @mw on freebsd-arm, AHCI_Q_NOPMP helps with this error:
(aprobe3:ahcich3:0:15:0): NOP FLUSHQUEUE. ACB: 00 00 00 00 00 00 00 00 00 00 00 00 (aprobe3:ahcich3:0:15:0): CAM status: Command timeout (aprobe3:ahcich3:0:15:0): Error 5, Retries exhausted
(note: this machine requires D25145 to attach the AHCI controller)