Can't save translations

Hi,
I’m trying to edit translations from; Theme panel > TRANSLATIONS > Translations.
After I entered a word/words on a box/boxes and clicked the SAVE SETTINGS button, the loading indicator will never stop.

Here’s some info;
– Newspaper Version: 10.3.9.1
– Using Japanese for default WordPress language
– This happens whether I type alphabetic characters in the box or Japanese characters
– I don’t use WP Super Cache and WPML

Is there any way to solve this?

Thank you!

Actually it gets 403 (and also the 8 tiles square indicator never stops) after I clicked SAVE SETTINGS button?

I got the reason, it was caused by the WAF. Now I can save them successfully.
Thank you!