How to improve my Ground contact time balance?

I can not help you here in specific (what side needs the work?!), but I can say strength training of both legs will be helpful in creating a strong base that allows for good balance and confidence in strides.  

Try to focus on single leg activities to help uncover weaknesses and imbalance.  Single leg calf raises (toe in and toe out as well ... "three-way calf raise"), can do leg press/extension/curls all one leg at a time.  One leg at a time lunge type stuff ... one leg glute bridge ... one leg side leg raises.  

If you do calf raises or squats with both legs at a time... it is very easy to favor one side (without knowing/noticiing it).  So with your goal of GCT balance... single leg work will be great!

For me, I know my left leg is 'weaker' ... so i purposefully ONLY do calf raises on that leg some days (during curl recovery time...etc).

I really cannot say anything about the accuracy, except that placement of the pod (off-center vs center) can have an effect. But if your easy run is more or less balanced, that sounds ok. My recommendation would be to do leg strength training in general. If you concentrate on one leg only, you'll risk just causing more imbalance to your running form.

Throw away the running pod and start to relax. Nothing is wrong with you.

Well, everyone can do what they want, of course, but seeing ground contact imbalance while running fast has helped me a couple of times to notice signs of muscle injury in time to do something about it. So I wouldn't be so fast in throwing absolutes.

Thanks for the reactions. Maybe some more information. For some months I had pain in the back of my knee (knee cavity). I noticed that I had more pain after I did some interval training.

My fysio said that this was because of injury in my hamstring and that it was stiff. After some treatments and many stretching of my hamstring it was a little better but not totaly gone. So now I was looking at my balance.

I'm already doing leg exercises for more strength because I indeed feel that my left leg is a little less strong. 

You can do your own gait analysis. Video yourself running - back view, side view and front view. Use slow motion mode to record, most phones have that feature. You can do that on treadmill or outdoors. Any imbalance should be easily visible on the videos.

This is the best advice. The difference you write is minimal. It could be a "rounding error", the sensor or the algorithm are not that accurate, and we are all asymmetrical, like we all have one leg longer than the other. Enjoy your runs and forget about this bs :).

Can you fix this if your legs are an inch are 1” difference in length? It’s literally efffected my hips and my back so, I’m assuming I can strengthen these areas but I have a lot of damage to them. It may be hard to actually do this. 

Well, I too am weaker on my left leg because my legs are different lengths. I’m wondering if o can even fix this issue. It has caused two meniscus tears in both knees. Those have been there forever. I haven’t don’t surgery. I just do squats. I have hip issues. I do need steroid shots periodically. I have severe back issues from it. So, I can try more workouts I don’t mind that but I can’t even wear heels. 

Nothing to worry about, unless the balance changes quicly. Pro runners often experience injuries or sickness after a negative change in balance.
Usually your balance improves as your speed goes up. Actually, your whole running economy goes up while running faster, which is kind of logical becasue the body adapt to higher demand.

As a performance coach i can tell from experiance and knowledge, that unilateral weighttraining is good for propreoception but doesnt make u stronger (fast) on one side. Isuggest you to inegrate some bulgarian split squats and Poliquin split squats and start with your "weak" side. Perform until failure and dont exceed the amount of excecuted reps for the "good" side. This can make you more balaced in time but dont expect a miracle.