Several minute delay receiving iMessages from another iPhone in same household?
Recently I upgraded from an iPhone 8s to a SE3, and shortly after this iMessages from my sister's iPhone (which I believe is an 11) have a 4 minute delay being delivered to me. However, if I respond and we begin a back and forth conversation, the messages send instantly as they are supposed to; it's only the first message of hers after we haven't texted for a few hours that seems to have this delay reaching me.
Our mother also has a recent model iPhone and there is no delay from her phone to mine, nor is there one from my sister's to my mother's, or mine to my sister's. As the title mentions we are in the same house, using the same service provider, same internet, and yet from less than 20 feet away the messages aren't being received properly.
This has been going on for months, so please don't suggest turning the phone off and on again as it has obviously been tried. I can't find any solutions online other than people suggesting to switch to SMS which doesn't address that there is clearly something going on here and I want to know what it is.
iPhone SE, iOS 16