Hi,
I have same kind of problem but I solved by editing the wp-config file with newly create table prefix.
eg: When you click on the database table prefix change button, then it change the table prefix with random generated its own, At the same time the wp-config file don’t have the write permission.( For security reason Wp-config file is not editable by wp security). So you have to do the manually by editing the wp-config file with random generated database table prefix.
This work for me.