[Shop-talk] Regrouting a shower.

[Obaa]

I'm rebuilding our shower door because it has started sagging.  While
scraping 
out the caulk, I noticed some of the grout has started
cracking/splitting 
between the tiles in the stall, so I plan on fixing those
areas as well.  Am I 
okay to just fix the broken areas, or should I really be
grinding out all of the 
old grout and re-grouting the entire shower?  I think
I know what the correct 
answer is, but it's a really big shower stall.... :)