Good catch and good repair.

It's sickening how much all this stuff costs but is still sometimes plagued with design problems to save an additional few $ in material and time over building something that will last and have strength above and beyond what it is expected to endure.

Sounds like some designers need to take a few more courses from certified welders about what types of welds and gussets are appropriate for different structural situations. 

Glad you caught this before it became a much more serious accident and/or repair. 

Will be interesting to see what sort of responses you get about it.