Had this error with a client and here’s how it’s fixed:
First, log into phpMyAdmin and make a backup of the eav_attribute table (use the Export option)
Then, click the SQL button and paste this into the box:
SELECT * FROM eav_attribute WHERE frontend_input=”weight”
Hit Go
The result should be one row, probably with an attribute_id of 101. Â Check that row and delete it.
This should fix your element_weight problem.
There are other mentions out there of turning off the weight option for simple products. Â That doesn’t fix the problem, just masks it. Â The above process will solve the error from happening again.