Switch to disassembly mode only works once. (CDB)

Steps to reproduce:

1. Debug a project, having set a breakpoint (e.g. the simple test app from the debugger tests)
2. When hitting the break point, switch to disassembly mode.
3. (optional) Step over a couple of instructions.
4. Switch back to source mode.
5. (optional) Step a bit further
6. Try to switch back into disassembly / single-instruction mode.

Expected result:
Switch into single-instruction mode is made, the little single-instruction icon gets activated and the source window shows disassembled instructions.

Actual result:
Switch into single-instruction seems to be made, the icon is updated, but the source code remains C++ only. It does seem that only single instructions are being stepped over when stepping, so the problem is that the disassembly isn't displayed.