Characters get stripped out when sending long Nepali (Hindi) messages

When large (more than 500 characters) message is sent in Nepali language, words at bottom of the message are damaged (some parts are removed). It is fine when sending less messages and even in large messages, the beginning words are fine.

This bug affects Hindi, Sanskrit and other similar languages. In our language there are characters widely used in almost all words:
ो, ौ, ,ी , ि , े, ै, ू , ु

These are the characters that gets lost. Alphabets are fine, they don't get removed. Without presence of these characters, our language can't be understood.

You can send any long Nepali or Hindi messages to test this issue or copy paste its content:  https://pastebin.com/raw/sZ3pLYYt and send the message. You can notice that at the end of the message, those characters are removed. 

Image: https://i.ibb.co/xLyBWq3/img.png