I tried to "Refresh" dependent fields (Multifield) at the admin panel but it keeps on loading, nothing happens.

When i try to check with the error log, it shows this error

27 Jun 06:37:59 | 4 repeats | Mysql Error: Too many keys specified; max 64 keys allowed on line# 2224 (file: /plugins/multiField/rlMultiFieldAP.class.php)

How can i fix this issue?

//I'm using 4.8.2 flynax version & 2.6.1 Multifield/Location Filter