I do not see a problem, however, look at the image at Vessel 3.3.0 submenu problems - #10 by tim_1 – this may explain what happens.
But this is an inherent problem with hover-based menus – visitor needs to be careful moving their mice…
You may alleviate this a little by adding an “extension” like the gray area on the screenshot below where green arrows represent valid mouse trails which would activate neighbouring menu items otherwise:
