RCS switching back and forth to SMS after 18.1.1 update

I’m using an iPhone 13 ProMax and having a terrible time with messages switching back and forth from SMS to RCS. I belong to a professional group chat that has had to be remade four times because it messes things up. I’m currently running 18.3.2 - and was hoping it would fix things, but it hasn’t.

Has anyone figured this out yet?