Let me start off by saying, the map looks wonderful, we need more good koth maps, and quite frankly, we don't have too many, so I decided to hop on a local server and give this map a go, trying out the map a bit.
You can open the enemy spawn room, also the 'BLOCKED' signs are outside the spawn door, instead of behind the spawn door:
http://cloud-4.steampowered.com/ugc/568898774538381923/CA147B99A109AAE5CFF8B7EE07BE515A21FFDEF2/
Example of a blocked sign on an official map:
http://cloud-4.steampowered.com/ugc/589161283254227897/37507C6EE22A014D65DBF76D21CAE1A0FCD7A178/
A weird 'see-through' bug that I'm sure isn't supposed to be there, also the place where I'm standing on, probably shouldn't be able to stand on:
http://cloud-4.steampowered.com/ugc/568898774538385051/4F0DC6B1C1EE0DDCBE7988CC2BC61572D839835C/
Don't see the point of this height advantage that promotes roaming soldiers standing on it trying to hide/get an easy bomb on the enemy medic:
http://cloud-4.steampowered.com/ugc/568898774538387056/6D768E2A81A7226971ADBAA6847022FCCC7BECAE/
Another spot you can stand on, and probably shouldn't, if you walk left you can spam the enemy spawn really easily:
http://cloud-4.steampowered.com/ugc/568898774538391787/23C6586EC2022418C85C38D5281CCAA93B1B7298/
And another one where you can hide on right above enemy spawn:
http://cloud-4.steampowered.com/ugc/568898774538410184/51B1E15AE889E49E2F0100176D5D10F0C9F8F15F/
Another spot you can hide on, and you probably shouldn't be able to:
http://cloud-4.steampowered.com/ugc/568898774538389293/71D62893F3E52CCDFA77F00D3C3DBEC11EAD6E09/
Two Sniper sightlines that you would probably need to play around with the spawn doors a bit more to get them just right, you're giving the team that has the point captured a some big sightlines that allow them to know where the enemy team is going to push them from, unlike maps like viaduct and coalplant where you would have to get into enemy territory (in coalplant the lobby area or far left, on viaduct you would have to hold quite close in order to know where are they pushing from), sandstone allows the team holding the point to know from where the other team is pushing by just holding on the point with having eyes on left and right.
http://cloud-4.steampowered.com/ugc/568898774538399159/E14306D90C2A724C5DF6A71C11639D3DAA492FE9/
http://cloud-4.steampowered.com/ugc/568898774538397275/B56E6D9BCE008BBC704F78AB68AFA68A2A84AD30/
A couple more spam angles that should be fixed:
http://cloud-4.steampowered.com/ugc/568898774538393662/F3F15B9BF106B4310C93EEB11F3359AC908218F7/
http://cloud-4.steampowered.com/ugc/568898774538395314/5E1DC27FD19133039FF1C1BA066E23DCB2A11595/
The capture point is quite large and probably should be adjusted so only ones who actually stand on the stone part of it can cap it:
http://cloud-4.steampowered.com/ugc/568898774538400996/B92D80B266AF5245EA90B123104FB94A8245647A/
You can also cap while standing on the fire stand on point for some reason:
http://cloud-4.steampowered.com/ugc/568898774538404018/F3E83289A4771954D69F482D75774B00AAB63730/
These stickies can kill the ones behind the net, which is kinda silly and not sure if intended:
http://cloud-4.steampowered.com/ugc/568898774538406364/ACA6257C4ACFAB47ECF7D91B675F369C8C9229BB/
Weird texture bug, not sure if its from my end:
http://cloud-4.steampowered.com/ugc/568898774538408356/129DE7B8E3EC6A4F0E3B92356BAE64F31CE607BC/
And this to showcase how lit is the map, which is really bright:
http://cloud-4.steampowered.com/ugc/568898774538412293/A73E23C4C654FDA98F960B89A3FAF0FE44792E8A/
And that's all, I'm sorry for the wall of pics but I think this was needed in order to improve the map, gotta say, I can see this map work but it needs some more playtesting and fixing, so keep up the good work dude, really loving the style of it.