I have my htc one m9 phone connected by usb to my computer. I was trying to copy pictures from the phone to my computer. I have two Dolphin windows open so I could drag and drop the pictures I want to copy. The first few times, it would fail. I didn't look too closely at the errors, but I think /var/log/messages might have logged
May 27 08:29:34 <hostname> kwin_x11: QXcbConnection: XCB error: 3 (BadWindow), sequence: 42839, resource id: 83886080, major code: 18 (ChangeProperty), minor code: 0
May 27 08:29:34 <hostname> kwin_x11: QXcbConnection: XCB error: 3 (BadWindow), sequence: 42843, resource id: 83886081, major code: 18 (ChangeProperty), minor code: 0
May 27 08:29:34 <hostname> kwin_x11: QXcbConnection: XCB error: 3 (BadWindow), sequence: 42847, resource id: 67108868, major code: 18 (ChangeProperty), minor code: 0

I went up a few folders, back, and then I was able to copy 1 file to my home folder. I then tried copying that one file to my original destination, and this time it worked. I'm not sure what was done differently this time that it worked, but it worked so I tried copying all the files. After a minute or so, I got a popup error message:
Unknown error code 150
Unspecified error
Please send a full bug report at https://bugs.kde.org
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I clicked retry and it looks like about 15 files got added to my destination folder, but it then gave the same error.
I had tail -f /var/log/messages /var/log/secure /var/log/audit/audit.log and I see in there
==> /var/log/messages <==
May 27 08:46:17 <hostname> audit: SERVICE_STOP pid=1 uid=0 auid=4294967295 ses=4294967295 subj=system_u:system_r:init_t:s0 msg='unit=lvm2-lvmetad comm="systemd" exe="/usr/lib/systemd/systemd" hostname=? addr=? terminal=? res=success'
May 27 08:46:17 <hostname> plasmashell: file:///usr/share/plasma/plasmoids/org.kde.plasma.mediacontroller/contents/ui/main.qml: QML Plasmoid: Cannot anchor to an item that isn't a parent or sibling.
May 27 08:46:17 <hostname> plasmashell: file:///usr/share/plasma/plasmoids/org.kde.plasma.mediacontroller/contents/ui/main.qml: QML Plasmoid: Cannot anchor to an item that isn't a parent or sibling.
May 27 08:46:17 <hostname> plasmashell: file:///usr/share/plasma/plasmoids/org.kde.plasma.mediacontroller/contents/ui/main.qml: QML Plasmoid: Cannot anchor to an item that isn't a parent or sibling.
May 27 08:46:17 <hostname> plasmashell: file:///usr/share/plasma/plasmoids/org.kde.plasma.mediacontroller/contents/ui/main.qml: QML Plasmoid: Cannot anchor to an item that isn't a parent or sibling.
May 27 08:46:17 <hostname> PackageKit: uid 1000 is trying to obtain org.freedesktop.packagekit.system-sources-refresh auth (only_trusted:0)
May 27 08:46:17 <hostname> PackageKit: uid 1000 obtained auth for org.freedesktop.packagekit.system-sources-refresh
May 27 08:46:37 <hostname> cupsd: REQUEST localhost - - "POST / HTTP/1.1" 200 187 Renew-Subscription successful-ok
May 27 08:47:05 <hostname> plasmashell: QXcbConnection: XCB error: 2 (BadValue), sequence: 37873, resource id: 67108868, major code: 141 (Unknown), minor code: 3
May 27 08:47:09 <hostname> plasmashell: QXcbConnection: XCB error: 2 (BadValue), sequence: 39074, resource id: 60817442, major code: 141 (Unknown), minor code: 3
May 27 08:47:09 <hostname> plasmashell: QXcbConnection: XCB error: 2 (BadValue), sequence: 39342, resource id: 85996931, major code: 141 (Unknown), minor code: 3
May 27 08:47:37 <hostname> PackageKit: refresh-cache transaction /2238_eaccbaeb from uid 1000 finished with success after 79401ms
May 27 08:47:38 <hostname> PackageKit: get-updates transaction /2239_dceeeded from uid 1000 finished with success after 993ms
May 27 08:47:52 <hostname> kwin_x11: QXcbConnection: XCB error: 3 (BadWindow), sequence: 62836, resource id: 85996931, major code: 15 (QueryTree), minor code: 0
May 27 08:47:58 <hostname> plasmashell: QXcbConnection: XCB error: 2 (BadValue), sequence: 45236, resource id: 85983236, major code: 141 (Unknown), minor code: 3
May 27 08:48:09 <hostname> kdeinit5: error() called twice! Please fix the KIO slave.

Reproducible: Always

Steps to Reproduce:
1. Connect phone by usb to computer
2. Try to copy files from phone to computer
3.

Actual Results:  
Unknown error code 150
Unspecified error
Please send a full bug report at https://bugs.kde.org
[Retry] [Skip] [AutoSkip] [Cancel]

Expected Results:  
Files get correctly copied