Database Collation

I am getting this fatal error on some pages: PHP Fatal error: Uncaught mysqli_sql_exception: Illegal mix of collations for operation ‘in’ in trp-ajax.php:154.

After some searching i found that its due to different database collation of some of translatepress tables.

wp_trp_gettext_el utf8mb4_unicode_ci

wp_trp_gettext_en_us utf8mb4_unicode_ci

wp_trp_gettext_original_meta utf8mb4_unicode_520_ci

wp_trp_gettext_original_strings utf8mb4_unicode_520_ci

wp_trp_original_meta utf8mb4_unicode_ci

wp_trp_original_strings utf8mb4_unicode_ci

So, 1. why do these tables have a different collation in the first place? Is it faster or something or its better for specific language?

2. Is the error really due to this? Can I just fix it by changing the collation? Which one should I keep to all of the tables?

I have used several times the fix database option on the advanced tab, and it always has problems and never ends. At least it was on staging site. So i am not going to use it on production.