Xibo Player 1.8.1 Lockups/Crashes

What kind of content is displayed on the player?

Are there any spikes like 90%+ in CPU usage for example?

There should be logs in the CMS for that player, you could also enabled auditing for that display (edit display -> advanced tab), that will create more logs.

If that would not be helpful, you can also carefully follow the instructions here - How to get a Windows Player log for advanced debugging