thunderbird-android: attached images cannot be displayed (but can be saved)

Expected behavior

After receiving a message with an attached image, I see a line for the attached part (jpg) with two buttons: “Open” and “Save”. Whether or not the image has been downloaded, I expect that pushing “Open” leads to seeing the picture full screen.

Actual behavior

I see a black screen with “No thumbnail” in really really small white type in the middle. The menu shows “Set picture as” and “Print”.

After doing this, or maybe just after downloading, I see a preview in the message. I have done “save” and verified that I can then use gallery to see the image from the sd card.

Steps to reproduce

1. Set up openkeychain and generate a key
2. get frustrated with clicking on approve for messages signed by weak keys (but not unsigned messages) and set provider to none (I have no idea if 1/2 are necessary; still fails with it turned back on)
3. Get an email with an attached image in INBOX. So far any sending MUA works, and in all cases other clients view the image fine.
4. Click “open”

Environment

K-9 Mail version: 5.111 (git master 5.111-15-gf388fe4 f388fe41b8992d8f80548e6c8124189895ae81f5)

Android version: CM 13

Account type (IMAP, POP3, WebDAV/Exchange): IMAP

adb logcat

09-27 19:16:55.377 6264-7884/com.fsck.k9.debug E/OpenPgp API: IOException when writing to out
    java.io.IOException: write failed: EPIPE (Broken pipe)
    at libcore.io.IoBridge.write(IoBridge.java:498)
    at java.io.FileOutputStream.write(FileOutputStream.java:186)
    at org.openintents.openpgp.util.ParcelFileDescriptorUtil$TransferThread.run(ParcelFileDescriptorUtil.java:78)
    Caused by: android.system.ErrnoException: write failed: EPIPE (Broken pipe)
    at libcore.io.Posix.writeBytes(Native Method)
    at libcore.io.Posix.write(Posix.java:271)
    at libcore.io.BlockGuardOs.write(BlockGuardOs.java:313)
    at libcore.io.IoBridge.write(IoBridge.java:493)
    at java.io.FileOutputStream.write(FileOutputStream.java:186)
    at org.openintents.openpgp.util.ParcelFileDescriptorUtil$TransferThread.run(ParcelFileDescriptorUtil.java:78)
p