trigger_capture error with FUJIFILM GFX 50R

First thank you for the wonderful library and your hard work maintaining it!!

Describe the bug With Fujifilm GFX 50R (newly added), capturing to sdram and no memory card installed. Capturing image and downloading works flawlessly with command:

gphoto2 --capture-image-and-download

see [section in reproducing error](#no-Issues-running---capture-image-and-download-ad-infinitum (practically)). I can run that command as many times in a row as I need. However, there are errors with trigger_capture.

Using gphoto2, only the very first time that I run the command:

gphoto2 --trigger-capture --wait-event-and-download=FILEADDED

will a photo actually be taken. All subsequent calls will fail. See issue with trigger capture in the section for reproducing the error (also there are links to the debug outputs). I have even tried deleting all files from camera in between successive calls to no avail.

Note that this is also the case when compiling and running the example sample-trigger-capture. Only the first time the capture is triggered will a photo be taken. The file isn't actually saved to hard drive though. Although the code does reach that execution path. However, all subsequent calls fail to even trigger the FILEADDED event. Yet I suspect the photo is actually being taken and stored in SDRAM.

Additionally, if I execute calls to:

gphoto2 --capture-image-and-download

after one or more calls to:

gphoto2 --trigger-capture --wait-event-and-download=FILEADDED

(with or without the wait-event-and-download) only the first executed command actually works to successfully download the file. See [this issue]() in section about reproducing the bug.

NOTE that I removed the extensive hex dump of the image data where it was available from the debug logs. However other than that nothing was removed.

I'm at a loss. Any ideas?

On a side note: Also, wondering if there should be a return here: https://github.com/gphoto/libgphoto2/blob/master/camlibs/ptp2/library.c#L5402. Otherwise ptp_initiatecapture() is called twice. I've added the return and compiled with and without that return and the symptoms are exactly the same.

Operating System MacOS High Sierra 10.13.6 (17G4015)

Name the camera

Model                          Port
----------------------------------------------------------
Fuji GFX 50 R                  usb:020,046

libgphoto2 and gphoto2 version compiled from source

gphoto2 2.5.20

Copyright (c) 2000-2018 Lutz Mueller and others

gphoto2 comes with NO WARRANTY, to the extent permitted by law. You may
redistribute copies of gphoto2 under the terms of the GNU General Public
License. For more information about these matters, see the files named COPYING.

This version of gphoto2 is using the following software versions and options:
gphoto2         2.5.20         clang, popt(m), no exif, no cdk, no aa, jpeg, readline
libgphoto2      2.5.22.1       all camlibs, gcc, ltdl, EXIF
libgphoto2_port 0.12.0         iolibs: disk ptpip serial usb1 usbdiskdirect usbscsi, gcc, ltdl, USB, serial without locking

To Reproduce

Issue with trigger-capture

Run gphoto2 --trigger-capture --wait-event-and-download=FILEADDED

file downloaded (as expected)

even though error displayed

*** Error *** 
PTP General Error
ERROR: Could not trigger capture.
Waiting for 'FILEADDED' event from camera. Press Ctrl-C to abort.
Saving file as DSCF0001.raf
event found, stopping wait!

trigger_capture_1.txt

Run gphoto2 --trigger-capture --wait-event-and-download=FILEADDED, again
- event never triggered no file downloaded trigger_capture_2.txt

Issue capture-image-and-download following trigger-capture

Run gphoto2 --trigger-capture --wait-event-and-download=FILEADDED
- file downloaded (as expected)
Run gphoto2 --capture-image-and-download
- file downloaded (as expected) capture_image_and_download_1_after_trigger.txt
Run gphoto2 --capture-image-and-download
- error
```
*** Error ***
PTP Access Denied 
New file is in location /store_10000001/DSCF0003.raf on the camera
ERROR: Could not get image.
ERROR: Buggy libcanon.so?
```
  capture_image_and_download_2_after_trigger.txt
  
  No Issues running --capture-image-and-download ad infinitum (practically)
Loop Start
- Run gphoto2 --capture-image-and-download
- file downloaded (as expected)
- Repeat Loop capture_image_and_download_1.txt capture_image_and_download_2.txt

As long as the photos are deleted from RAM we are good to go. Once 6 are in memory it can no longer work. I am shooting RAF files at around 110mb each.

gphoto / libgphoto2

trigger_capture error with FUJIFILM GFX 50R #366

Issue with trigger-capture

Issue capture-image-and-download following trigger-capture

No Issues running --capture-image-and-download ad infinitum (practically)