mobile network – Intermittent failure to receive SMS and MMS messages

I noticed an issue in mid December where a few messages in a row that were sent in a group MMS were never received on my phone. A few days ago, I had the same issue with an SMS message sent to me. There may have been other instances as well that I’m unaware of. In December, my default messaging app was QKSMS. In the instance a few days ago, my default SMS/MMS app was Signal.

I’m using an Asus Zenfone 6 on Wing’s AT&T network (for those don’t know, this essentially means Wing bought AT&T contracts in bulk and is reselling them individually).

I don’t know of any issues with outgoing messages. The intermittent nature of this problem makes it difficult to troubleshoot. What steps can I take to ensure I don’t lose any incoming MMS or SMS messages in the future?