Why do my texts sometimes never get delivered to this phone?

My phone is an iPhone 7. "Send as SMS" is turned on, "Send and Receive" is set only to my number. Verizon.
My girlfriends phone is an Android Cricket Wireless - ZTE Grand X 4, and she uses Textra as her texting app.
She never had an iPhone before.

This seems to only be a problem with our texting.

For most of the time, our texts go through totally fine. Every now and then though (rarely), she will slowly start to not receive some texts. It will start with a lost text here and there, and eventually almost no texts at all will go through from my phone to hers, and we resort to Snapchat to communicate. I still receive all her texts, and over time she starts receiving my texts again. I went to a Verizon store about this and they couldn't quite figure it out.

Neither of us want to reset our phone, we would just like to figure out why it does this so we can fix it directly.

How do I unlock an iphone 5?

I have a contract with Tesco mobile which included a phone which I subsequently broke!

Rather than pay for quite an expensive repair, a friend of mine very kindly gave me an iphone 5 they were no longer using.

However, when I put the Tesco mobile sim into the iphone it rejects it.

I'm told I need to unlock the iphone but I have no idea what that means or how to do it.

If anyone could help I would be very grateful!

How to block iPhone 6?

Is There a way to block JUST text messages on iPhone, but still receive calls from the person? Or at least to silent anything they send like in fb messenger?

What phone should I buy?

Me and my misses are in need of new phones (currently we both have iPhone 6)

I've been looking at the Sony Xperia z5
And the Sony Xperia XA

Looking to spend under $200 (don't need top of the line - just decent)

What would you guys recommend we get?

How do I log in to the Spanish Dict App?

There's no button or option to log in for the current app version on my iphone. I already checked everywhere for it in the menu, and logging in on Safari doesn't login for the app either.

Macbooks and iPhones with personal hotspots?

So I noticed on my macbook that when I click the Wi-Fi icon, my iPhone pops up and I can activate a personal hotspot from the laptop. This might be a big concern for me; if, for example, I'm in an airport, can a random person with a macbook activate a personal hotspot from my phone without me knowing? Or is it specific to my laptop since my phone has synced to it multiple times?