Hello,
Sorry for my poor english.
I’m using DHtmlx 3.6.
when I use dhxLayout and attachGrid with splitAt() method,
progress appear like attached image.
progress doesn’t appear in the left side of the fixed column and shows only white background.
Most probably issues caused by too small z-index value in CSS. You can check the styling of progress layer through dev. tools and add extra CSS class on the page to increase z-index of the progress layer.
Unfortunately, version 3.6 is too old and not supported anymore, so I can’t provide any patch.