MAMEWorld Forums - EmuChat - MAME cfg file <video> tag not persisting

In MAME, (a recent version, 0.146u5), I am having problems with video modes not 'sticking'.

Here is the problem:

Start mame to play a game such as Marble Madness (mame64 marble)
Set Video Option to 'cocktail'
exit MAME
Observe new file 'marble.cfg' in cfg directory:
{?xml version="1.0"?} {!-- This file is autogenerated; comments and unknown tags will be stripped --} {mameconfig version="10"} {system name="marble"} {video} {target index="0" view="Cocktail" /} {/video} {/system}
Start MAME a second time (mame64 marble)
Observe the game started in split screen cocktail mode as it should
exit MAME
Observe changed file 'marble.cfg' in cfg directory - this is wrong
{?xml version="1.0"?} {!-- This file is autogenerated; comments and unknown tags will be stripped --} {mameconfig version="10"} {system name="marble" /} {/mameconfig}
Start MAME a third time (mame64 marble)
Observe the game started in default video mode (not split screen cocktail mode)

So the video tag in the cfg file is getting read, but not written correctly.

Is there any solution to this problem? Am I missing something? I might be able to hack a fix by write protecting the correct cfg file, but hoping to avoid that.

TIA, Gary