Texting from pc to xfinity mobile phone results in multiple text messages received

I brought this up in 2018 and it was never resolved so here I am again. 

When I text my hubby from our home pc using xfinity.com>email>text to his Xfinity mobile phone he gets 10-12 copies of the same text message.  This does not happen when I text him from my Xfinity mobile phone to his or from my pc to anyone else's mobile phone that is not on Xfinity mobile. Its very frustrating.

We have cleared his cache on his phone, etc,etc but it does not fix it