blackstonekeep.com

Found that its possible to forge above level 40 without the warning/stop from the mystic forge golem.

This happened today with a certain color forge stone that adds On Hit properties to weapons, etc. Item was level 36, golem let me use that forge stone without issue, final item was level 43.

The on hit added in this case was Slow at CL 9.

-Gohaken

In fact, level protection is implemented not a lot of time ago. Early you was able to got 41+ requirement without any warning. This functionality allow to avoid well-known mistakes. But not everything is so easy as looks.

IMHO, it is not fatal issue. You can cancel enhancement.