Which app exactly are you talking about? iOS? Android? Window beta version? MacOS beta version?
I only eve use the WiiM Home app for Android on a couple of smartphones (no tablets) and I cannot remember the last crash.
Re-indexing the USB key on my WiiM Amp did not complete successfully and erred out with a "connection problem". It turned out I just had to power cycle the Amp after the latest firmware update and it worked flawlessly again.
So, if you encounter any problems that look like they are app related, don't just reboot your phone and clean the app cache (if possible on your platform). Also remember to restart your network devices and to remove your WiiM from the mains power for a minute once in a while.