Dropdown menus disappear on selection of nested submenu/blurry interface

[iamcyanblue]

I'm on Mac OS 14.5 Sonoma and running the latest version of SoundLoomE.
I'm having issues when clicking on dropdown menus, and mousing down the list of menu items. If a menu item is a nested submenu, the whole dropdown menu vanishes after mousing over the nested menu, and then mousing off it again.

E.g. I can mouseover all menu items in the "Workspace: Selected Files of Type" menu from "DO IT AGAIN" to "Play Merged Channels". But if I mouseover "Add Replace, or Find Sndfile(s) in Mixfile" and then move my mouse back to any top-level item (e.g. "Play Merged Channels"), the whole menu disappears.
However, the menu is still there, the screen isn't drawing it. If I mouseover the part of the screen that should contain another nested menu within the same menu, e.g. "Post Display of File(s) on Desktop", the whole menu briefly flickers on again.
Is it something to do with the version of Tcl bundled with Sonoma MacOS 14?

I've also noticed that the interface text is very blurry, like a low-resolution image that's been heavily anti-aliased. Is there any way to sharpen it up (playing havoc with my dyslexia!). Changing the large screen/small screen option in System State doesn't have any effect (I can't choose the Leeds colour scheme either).

[iamcyanblue]

Additional: my installed version of Tcl is 8.5.9