tracker issues in fusion

I reckon it might be me being tired from the whole day spent working on DVR, it might be me being noob, but i just know since i bought this software i feel so very often like a freaking ping pong ball between moments of super excitement for the potentiality of this software and the huge frustration for what really seems like annoying bugs just coming out of nothing and for which i have no explanation neither workarounds (unless i redo everything from scratch which can be seriously turning off any motivation).
Enough of me moaning. Here's the example of one of these situations: i'm working on a short clip in which i just wanted to change the color of the eyes of the subject while it moves. It's something i already did in the past, but just to be sure, i followed another tutorial anyway as i still need time to get the hand with DVR. So i track the first eye, color it. Fine. The tutorial ends saying "do the same thing for the other eye", obviously. There's no need to make a tutorial for the same stuff right? And i agree. So i basically copy the procedure and immediately the mess starts...
The tracker doesn't track a damn thing for the second eye, and it also makes the first eye tracked losing its data. Yes, i did create a new track on the list. Yes, i did try adding a new tracker node to do everything from scratch. No matter what i do, it doesn't work. Not to speak about the green tracker with the target, disappearing as soon as i click and drag it to adjust it, making the adjustment really difficult and not precise. If i go and start a new project, i can see the tracker target with no probs.
These things drive me crazy cause they apparently have absolutely no rational explanation.
I'm at a loss honestly. If it's me being dumb, please tell me and possibly help me sort out this situation. Thanks for your patience
Enough of me moaning. Here's the example of one of these situations: i'm working on a short clip in which i just wanted to change the color of the eyes of the subject while it moves. It's something i already did in the past, but just to be sure, i followed another tutorial anyway as i still need time to get the hand with DVR. So i track the first eye, color it. Fine. The tutorial ends saying "do the same thing for the other eye", obviously. There's no need to make a tutorial for the same stuff right? And i agree. So i basically copy the procedure and immediately the mess starts...

The tracker doesn't track a damn thing for the second eye, and it also makes the first eye tracked losing its data. Yes, i did create a new track on the list. Yes, i did try adding a new tracker node to do everything from scratch. No matter what i do, it doesn't work. Not to speak about the green tracker with the target, disappearing as soon as i click and drag it to adjust it, making the adjustment really difficult and not precise. If i go and start a new project, i can see the tracker target with no probs.
These things drive me crazy cause they apparently have absolutely no rational explanation.
I'm at a loss honestly. If it's me being dumb, please tell me and possibly help me sort out this situation. Thanks for your patience