Well, warranty won’t be based on installation orientation alone, but it depends on the issue. If your unit is experiencing a spurious overload, and it’s installed face down, there shouldn’t be an issue with warranty because the one isn’t affecting the other. If the transformer shakes loose and it’s installed face-down, there will be an issue with warranty, because the one is affecting the other.
If you sign up for a (free) account at professional.victronenergy.com, there are an absolute load of training videos and resources available through there that will be exceptionally useful, both in learning more about the components, best practices, and in some cases the internal construction of units that will help in making judgement calls about such things.