Armando – not sure if it’s just me, but workouts recorded by the mobile player seem to show “zero” duration on the table summary, even though there is an elapsed time recorded in the workout. See screenshot attached. Capture
Our latest XM update addresses this.
I was experiencing this, too.
It started at the beginning of February 2017, or so.
Until now, I had to manually delete the Xert recording from Xert Web App and manually upload the .FIT files recorded by my old trusty Edge 800.
Not a big issue but a bit frustating, nonetheless.
Glad to hear you fixed it! 
For those who may concern - You can now (re)upload your past workouts from XertMob to Xert Web App and they will beautifully show their correct duration! 
(Tried for myself and it worked!)
Thanks.