Crack in Barn Door - Is this a problem??

Yeah but $400 for a door and zero guarantee that it won't happen again....Hopefully my welding skills will hold up to a 35...

To me it looks like a gusset plate needs to be made with the same profile about 100mm and fully welded in.
As Mega suggests remove the rubber and glass, sand it back to bare metal and tack in the gusset then fully weld .
OR,,, you could weld as is and quench the weld with a very wet rag as you weld small bits at a time.
This may save a lot of time and have you back on the road earlier.
To me this would not hinder door seal or the way it closes

I didn't remove the glass. I just took my time at welding it up so it wouldn't get too hot. I did make a very strong brace for the inside of the door skin.
Nearly finished, just about to apply the clear coat then I'm done. I will start a new DIY thread soon on this for other to see....