Skill ring upgrade

When I went to upgrade my R skill ring from level 1 to 2 and says safe but it failed on the first upgrade. When I read online it says safe status is 100% none fail.

"Certain" in green is 100%, while "Safe" in light blue means 80%-99%; Rings specifically (with the exception of Valor Rings) have an 80% success rate at every level, so you can use Enhancement Aides (not Great Enhancement Aides) to increase your success (I believe you can get the +30% ones from the ExCube Shop).