Contact names not syncing with messenger app - LG v30+ (Sprint)

[PowersLM]

On my LG v30+, in the default Android messaging app, the names of some of my contacts do not appear in the main list of conversations and only the number is listed. When I open up a conversation, the first letter of the person's name shows in the circle next to their texts, but the heading of the page is still their phone number. If I go into "people & options" within the conversation, it shows their name along with their number as if there is no problem at all.