[Vuejs]-Why some sites load like an SPA while some refreshes everytime?

The app on Render is indeed an SPA, the Railway one behaves like an MPA.
I can confirm that.

As of the exact reason, we’ll need to check some of your code. What matters the most is how it behaves if you bundle (and preview) it locally.

Also, depends if you use 'server' or 'static' for those as a target.
Also how you configured the deploy on each platform.

PS: I would start by fixing those errors first is quite important.