SMS to MMS conversion problem with S8

[Android Central Question]

A few weeks ago I noticed my texts converting to MMS after only a few words (emojis seem to make this worse). Used to be able to send way over the 160 character limit with no issue. Problem is the message will send and be received but always displays "no subject" (where a regular text will always display the first few words). The receiver will have to actually open the message to see what it contains. I have two other S8s in the family and this issue doesn't happen on them. I compared settings on the known-good phones and they're identical. I did a factory reset on my phone this weekend and was unable yo fix the issue. Using the stock message app and keyboard, all software is up to date and identical to the other phones. I just want the stock app to work as it does on the other phones and as it did on my phone up until a few weeks ago.
Thanks in advance...

 

[ManiacJoe]

S8
stock messaging app
stock keyboard

Are the "good" and "bad" phones using the same carrier?

 

[B. Diddy]

Welcome to Android Central! Are you using the stock emojis, or were you able to add 3rd party emojis? If the latter, then I wonder if that might be forcing the conversion to MMS.