Added even more detailed logs. Thanks to today's reported logs I already know that bug happens because some materials can't be read by Unity. With this build I will know more detailed reason why this is happening. Make sure the game's build is 0.3.5.4111 or newer (version is displayed in bottom right corner of a screen).
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I will copy/paste text from previous patch notes below so if you experience the "Loading" bug you can help me fix it.

After this update when you start Mirage from Steam client - you will get two additional launch options:
* Play Mirage (DEBUG-Desktop)
* Launch Mirage (DEBUG-VR) in Steam VR Mode

When you launch a game in DEBUG mode it will record all errors in this file: mirage.rpt
This file is located next to Mirage.exe. On my PC it's here:
D: Games Steam steamapps common MirageByMorganaVR mirage.rpt

Please send this file to my email at morganavr.mirage7@gmail.com and I will deal with this bug once and for all.