Brake fluid is hydroscopic, it attracts water. Flush it out and use a new sealed bottle of fluid. Ensure your MC seals are good.

 

MC seals?

 

Master cylinder

 

Thanks

 

Get it solved?

 

I think the MC seal is OK.
Probably I will replace the brake fluid today and I tel you if is solved.

Thanks for your help

 

Brake fluid replaced, left caliper released micro air bubbles in the bleed process...
But I don't have time to test it in the next days, Saturday is the day...

 

Good deal. I recommend that you also check that the front wheel is installed and centered in the calipers correctly. It's easy to get it wrong. Check out this video for a good procedure to reduce installation errors. Principles are the same on your bike.

 

Excellent...
I will do the same next Saturday
Thanks

 

Apparently the problem is fixed.
I bleed the system with new dot 4 urbf fluid and did a little aggressive ride to test... I think is solved
Thanks for your help