Contact names disappearing in messages

Hello, I have an iPhone 6 (just a plain 6) and I have recently updated to 10.2.1. Lately, I've noticed that occasionally the names of several of my contacts in the messages app have disappeared, leaving only the phone number. It only happens sometimes and seems to be random. They'll be there one minute and then the next they'll be gone, then they'll be back etc... I think it is also the same contacts usually. They are newer contacts as well and have only been in my phone for some months whereas the contacts whose names aren't erased are ones I have had for a year or longer. It's not a huge deal but it is rather annoying seeing as I don't memorize others' phone numbers anymore. Here's a picture that shows exactly what I mean.

Any fixes?

Also I don't know if I am putting this in the right place. The subforum organization here is confusing.