Hi Scotty,
I've just had a look at the code and done a test run. It looks like the script isn't explicitly closing the bank. The reason the bank is being closed manually is the OSBot walking code (which is called immediately after the inventory is configured) will close open interfaces (bank included) before setting off. To prevent this, I had a look at the WalkingEvent API but couldn't see any functionality to disable the feature. As a result, it is not feasibly possible to prevent this unfortunately (an alternative would be to implement my own walking code, but this would result in sacrificing reliability - also reinventing the wheel is always a waste of time!)
If you are finding that the script is closing the bank with the mouse, you can always enable the 'esc to close current interfaces' option in the osrs settings tab (shown below). This will streamline the process.
Sorry about that - hopefully you understand!
Best
Apa