Android apps built with Solar2D version 3700 and later crash when the Android navigation button "Recent Apps" is pressed. (The button next to the home button that looks like three pipes.)
Chodongwon82 has a detailed explanation of the problem, complete with video, on the forums:
https://forums.solar2d.com/t/when-pressing-the-android-recent-apps-button-iii-the-app-unexpectedly-crashes/357146
This may sound like a trivial problem, but it is recorded by Google as a crash, and a high crash rate can result in the Play Store lowering the app's discoverability through search and will have real consequences for the app's success.