The marketplace is just that, a marketplace. As anyone who has been using flight simulators for a long time will tell you, addons can inadvertently cause problems, but most developers are responsive and will help resolve your issues. There are pros and cons to buying from the marketplace, but it’s more a convenience thing. It shouldn’t put you off though. I’d suggest try one addon at a time. That way you can narrow any issues down to the last change you made. Hope that makes sense.