You cannot totally test everything (This is also why Bubble release can create issue for some apps).
A) You can have conflict with another plugin
B) There’s so many possible settings in Bubble (mostly related to layout) that could affect element plugins
C) Common error: plugin element is hidden and the user run an action while the plugin is not ready. You can catch this error by checking if the element ID is on the page or not
D) Are you sure this is an error and not an incorrect configuration from user? Better documentation on how to use plugin will help