Sometimes an addon can conflict with other addons. RealUI is primarily tested as it's own package, so any error may be the result of a bad interaction with another addon.
Also, be sure that you have the most recent version of all your addons. If the other addon as an alpha or beta version, include that in the report.
2. Check for errors.
Check the far left icon on the Infobar, if it is a red bug icon you have one or more errors. Type /error to open the error log.
If the error includes [ADDON_ACTION_FORBIDDEN] or [ADDON_ACTION_BLOCKED], follow these steps:
Get to an area where you can get this error and enter /taintLogging into chat. Do whatever it is you're doing to get the error, then type /taintLogging again to stop logging.
Once that is done, go to World of Warcraft\Logs and find taint.log. Put the file into a zip archive and attach it to a post.
3. Get the debug log.
The next time you get that error, type into chat:
where <RealUIModule> is the relevant module eg. AuraTracking, Config, UnitFrames, etc.
Click the page icon on the upper right, and reload the ui (/rl). Navigate to World of Warcraft\WTF\Account\<YourAccount>\<YourRealm>\<TheToonYouWereOn>\SavedVariables and find nibRealUI_Init.lua. Put that in a zip file and attach it to a reply.
4. Is there any other relevant information?.
If it's a display issue take a screenshot.
Does it only happen on a specific class?
When does it happen?
5. Can this be reproduced reliably?
Reload the UI (/rl), and keep track of what you do until you get the error again.
6. Search the forum for a similar issue.
Reply with the information gathered above. Use [code] tags for errors and logs.
If there isn't a thread with your issue already, make a new one. Make sure to use a title that describes your issue.