Let me set some context for answers before we deep dive into the solutions -
I hope you visited this articles since my answer will be using them for context. As xas is a Mendix api called by Mx client to communicate with Runtime, the order of call I suppose entire depends on the page design (mainly order of data source containers come into the picture).
To control this behaviour, you need to inspect each xas and check "action" field under payload and the check "request" and response for each xas requests, you can automatically able to adjust this.
Now coming to stalling, as per stack overflow article there can be various reasons which can cause this, so after re-structuring your page design, see if stalling problem still persists. If yes, check for queueing timings as well.
Hope this helps.