can't 'continue' after 'next' in breakpoint's commands/end block

Hello, I'm trying to debug KWin window manager,
to not halt the session it can't be paused so I created such script to
trace function calls:

$ cat ~/kde/gdb-x
set pagination off

break KGlobalAccelImpl::x11KeyPress(xcb_key_press_event_t*) 
break TabBox::keyPress(int )
break /home/bam/kde/src/kde/workspace/kwin/src/tabbox/tabbox.cpp:555

commands 1-20
# FIXME: for some reason KWin halts on any stepping command here, ideas?
#next
continue
end

continue &

I'm attaching to a KWin process such way:

gdb attach $(pidof kwin_wayland) -x ~/kde/gdb-x

The problem is I can't insert next/step and such commands in the
breakpoint's 'commands' block - the process halts just after the 'next'
there despite the presence of 'continue' command afterward.

So I need to switch to another VT and kill gdb process to bring my
session back.

I'm not quite understand why it happens and what I can do with it. Any
ideas?