Game maximising into fullscreen mode?

[selkieseeker]

When tabbing back to a game (webfishing in this instance), it seems to be going into fullscreen mode rather than simply re-maximising the borderless window. The game settings will still say borderless window, however my pc's flyouts (e.g. when changing volume) won't come up when in fullscreen mode, and this same issue occurs when borderless window helper re-maximises the window, so I can only assume it's making it fullscreen in some fashion. If I go to the display menu, open the options dropdown, select borderless window again, and confirm the settings, flyouts work again. Is there any fix for it maximising in another mode?