Clip zip "Buttons locked" message

[YYzz]

Hi. Everybody

I am using the Rockbox 3.13 on a Sansa Clip Zip (recently switched from Clip+)
I have one question, or a suggestion of an improvement.

Whenever I use the button lock feature, I detect a small portions of some left over pixels of the "Buttons Locked" or "Buttons Unlocked" message on the WPS display.
(this didn't happen when using Clip+)

I guess this is somewhat a "theme" dependent topic. Some pixels of the message will be wiped out, as the WPS display viewports are overwritten, but those areas that weren't refreshed seems to maintain the pixels of the "Buttons" message.

It is not a serious issue at all: obviously just a display issue, and also if you go back to the main menu, and then again to the WPS the remnant pixels will be totally overwritten. But it is annoying if you want the keys locked (the WPS stays messy while it's locked! )
Can somebody suggest a workaround or a cause for this issue?

best regards

PS: I don't know how to save the screen image so I am sorry I can't send an example