I too have confirmed the problem of not being able to write. It seems that my confirmation was insufficient.
It seems that this problem occurs when connecting DAPLink_XIAO and brick_XIAO directly with wires. However, when brick_XIAO is put on the XIAO expansion board and connected to DAPLink_XIAO, it can write without any problem. The cause is still unknown at this point.
By the way, if you use ST-Link instead of DAPLink_XIAO, even if you connect directly to brick_XIAO You can write without any problem.