When we encounter issues that only happen on certain devices, versions or ROMs, we often don't have the right phone in our tiny little test lab as there are over a thousand Android devices on the market. When we're not certain a fix will work at all, we often ask if you could install a test version from an .apk.
An apk file is basically an app in an installer, we usually send it as an email attachment. When clicked on the phone or tablet, it shows a permissions dialog and an option to install it.
For security reason, the option to install from unknown sources outside Google Play is not enabled by default. If you haven't change that setting, go to your device's Settings screen, go to the Security section, and scroll down and enable the Unknown sources checkbox.
The test apk we send out are properly signed releases, they will be automatically replaced by updated ones from Google Play once they are available. If you don't have any issues you can keep using it until the next release.