Sony ILCE-6400_capturemode_issue

Hi,
First I set my camera as "Bracketing C 2.0 Steps 5 Pictures" on the camera body(not gphoto2 command, and camera is off line)
This means "Cont. Bracket 2EV*5steps", such as 1/1000-1/250-1/60-1/15-1/4sec set.
And powered-off, hooked the camera to my RasPi, powered-on the camera, and shot by command;
$ gphoto2 --capture-image
I heard 5 exposures as I expected. 
gphoto2 says, dawnloaded as capt0000.jpg to capt0004.jpg, but I got no data.

Next shot by the same command, I heard only single exposure with no data, but gphoto2 shows the message as capt0000.jpg
(not as capt0005.jpg)

gphoto2 still shows;
$ gphoto2 --get-config capturemode | grep Current
Current: Bracketing C 2.0 Steps 5 Pictures

I hope the solution on this issure, thanks.

Best regards,
Tatsuji
p.s.
My system is as shown bellow.
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$ uname -a
Linux raspberrypi 4.19.118-v7+ #1311 SMP Mon Apr 27 14:21:24 BST 2020 armv7l GNU/Linux
(RasPi3B+, 32GB)

My gphoto2
$ gphoto2 --version
This version of gphoto2 is using the following software versions and options:
gphoto2         2.5.23         gcc, popt(m), exif, no cdk, no aa, no jpeg, no readline
libgphoto2      2.5.24.1       standard camlibs, gcc, ltdl, EXIF
libgphoto2_port 0.12.0         iolibs: disk ptpip serial usb1 usbdiskdirect usbscsi, gcc, ltdl, EXIF, USB, serial without locking

My camera(Firmware_ver=2.00)
$ gphoto2 --auto-detect
Sony ILCE-6400 (PC Control)    usb:001,012  

My capture mode=27
$ gphoto2 --get-config capturemode  | grep Current
Current: Bracketing C 2.0 Steps 5 Pictures
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