TMS320F28377D: Become a low-power mode When I lock a DCSM

Hi all,

I would like to know why the following phenomenon occurs.

1. Start Uniflash (v4.1)
2. Enter the password in PSWD 0~3 of the Uniflash GUI and unlock it. (Because my device uses DCSM)
3. Unlock will succeed at this time
4. After unlocking, if I lock it immediately, the following image error will be output

I read TRM, but I could not find a reason to enter low-power mode
Does anyone know about this reason?

Best regards,
Sasaki