Inconsistency in Star Trek? I'm Shocked!
Actually It happens a lot, both within series and between individual series. Putting up with these Inconstancy is part of the game if you wanna have fun being a Star Trek fan.
As you grow in your fandom, try to remember this... It's a quote from Dr. McCoy to Mr. Spock about questioning the lyrics of the Song, Row Your Boat. Spock stops the song and says "Life is not a dream." McCoy: "It's a song, you green blooded Vulcan! The words aren't important, what's important is you have a good time singing!"
Try to place importance of the story you are watching at the time over how well it aligns with any earlier or later continuity. Star Trek is wonderful! Marvelous! We love it sooooo much! But, it is not a religion! It is not perfect, it has flaws and we have to live with them. If you cannot, then your life as fan is going to be pretty miserable if all you ever see is the warts
All that said, sometimes the pain and suffering of an inconsistency (Continuity Problem) can be reduced with an application of some 'head cannon explanation'. We can think up some kind of explanation that puts a patch on the problem. These ideas are not canon, they are personal fixes in our heads for issues, but what works for you may not work for everyone.
Sometimes the producers "RETCON" a problem. It stands for "Retroactive Continuity" If a problem gets RETCONED by the makers (owners) that means that a later episode has given an official patch for an earlier continuity problem.Whenever episodes have a continuity problem the later trumps the former!
In TOS the Romulans did not have forehead ridges but later in TNG they did. "Which is it?", raged fandom for years. Then, a recent episode of Picard solved it with a single sentence. Romulans with ridges are "...from the north."
TL;DR Don't worry about it!