1) Please install our Helix-3 quick start pack
2) Go to its front end and click on the offcanvas menu little icon (see my screenshot 03.png) and in response you will see the offcanvas menu nicely displayed (see my screenshot 05.png)
2) Log in to the back end and open the module manager
3) Under the filter "- Select Position -" select "offcanvas" (see my screenshot 01.png)
4) Once in response to your click on the "offcanvas" in step 3 your list of displayed modules changed to two modules ("Search" and "Off Canvas Menu", unpublish both of them (see my screenshot 02.png)
5) Go to your front end and click on the responsive menu icon (see my screenshot 03.png) - you will see reproduced that very error message that you faced
6) Go back to your Joomla module and publish the two modules, positioned on the "offcanvas" positon
7) Repeat step 5, only this time instead of that error message you will see two off-canvas modules.