Why am I missing some Android group texts on my iPhone?

Jerdog wrote:

I have a few people in a group text thread: myself with an iPhone on AT&T, another person with an iPhone on Verizon, another person with an Android on AT&T, and someone else with an Android on Verizon. I only get a small percentage of the Android on Verizon's person's group texts, but I get everyone else's. There is no apparent long-term rhyme or reason that I can point to for not getting all of one person's group texts. My friend's Android on Verizon phone is 3 years old, but it says it doesn't have any updates and there have been no updates on it since 2023 which is weird. Could that be the issue? I have done everything I can to figure out why this is: deleted the thread, signed out and back in to my Apple account, and restarted my phone. I can't figure out what is going on. The only thing I can point to is that I stop getting his group texts after I get an update for my phone. Then a few months go by without getting his group texts until I get one out of the blue. I do get his direct to me texts.

Any adea what could be the cause or do I just have to visit an AT&T or a Verizon store?

[Re-Titled by Moderator]

MMS is a phone carrier feature, report the issue to AT&T.