Bug 517112

Open Dolphin.
Navigate to a local folder and select files/folders.
Drag them (or use Copy/Move) to a mounted or directly accessed Samba share (smb://…).
The operation triggers an immediate or near-immediate crash of kioworker and frequently plasmashell as well.

Workaround in Use
I have switched to mounting the same share via sshfs and performing all file operations with Midnight Commander (mc). This completely eliminates the crashes — the system remains fully stable, and only terminal-based workflows are required for network transfers.
This is quite disruptive for daily use of the KDE desktop, as it forces me to avoid Dolphin entirely for any Samba-related work.

Why this is happening (explained simply and from multiple angles)
The involved pieces:

Dolphin = KDE’s graphical file manager.
KIO (KDE Input/Output) = the framework that handles all network, remote, and even some local file operations.
kioworker = the separate background process that actually talks to the Samba server (the “smb” worker).
plasmashell = the desktop itself (panel, wallpaper, notifications, etc.). It sometimes gets pulled into the crash because it listens to KIO events for progress notifications or clipboard handling.
Samba share = the Windows/Linux network folder you’re writing to.

When you move files in Dolphin to an SMB location, KIO’s smb worker has to:

Authenticate.
Copy the data.
Delete the source (for a true “move”).
Report progress back to Dolphin and the desktop.

Any crash, assertion failure, or unhandled error in that worker can bring down the whole chain — including plasmashell in many reported cases.
Root cause (most likely)
This is a long-standing family of bugs/regressions in KDE Frameworks’ KIO SMB implementation, especially noticeable in Plasma 6.x on Arch. Similar reports (crashes on connect, during listing, or during write operations) have appeared throughout 2025 and into 2026. Some were fixed in Frameworks 6.16 (connection crashes) and 6.19.1 (copy/rename “access denied” regressions), but file-move operations and the resulting kioworker/plasmashell instability have persisted for some users depending on exact server configuration, authentication method, or share setup.
Your sshfs + mc workaround perfectly sidesteps the problematic code path:

sshfs uses the much more stable sftp KIO worker (or pure FUSE).
mc does raw file I/O without involving KDE’s graphical KIO layers at all.

That’s why “only Yakuake keeps working” — everything else that touches the desktop shell or KIO gets destabilized.
Nuances & edge cases:

Direct smb:// URLs in Dolphin are often worse than pre-mounted shares.
Moves are more crash-prone than pure copies (because of the delete step).
Large numbers of files or bigger files increase the chance of hitting the bug.