This is likely caused by a theme/ plugin conflict.

The best way to determine if the issue is being caused by a theme and/or
plugin is to temporarily switch your theme and disable all plugins. Finally,
test to see if the issue is resolved by checking to see if the error is gone.

To figure out which plugin is causing the problem, continue to the next step
reactivate your other plugins one by one, testing after each, until you find
the one causing conflict.