Missing or surplus Incoming character

Hello.
Sometimes I receive Incoming SMS with Missing or surplus character from previews SMS in UTF-8 Messages.
Sometimes several characters from the previous SMSs with the new SMS are added to the end of the sentence.
What can I do to fix it?
which logs I must leave here ?
thanks.

In this picture I show surplus words to add in next SMS.
Green is Original Messages and Yellow is surplus words from previous SMS

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