Ranges from small nitpicky annoyances to potential issues.

There is visible nodraw next to the bath in blu spawn in the corner of the room if you look down.
setpos -36.007038 -4460.550781 -127.968681;setang 83.926277 -92.985634 0.000000

The roof corner pieces that stick out of the blu spawn roof aren't clipped off.
setpos -998.018799 -2744.099854 130
setpos -1796.126343 -2915.878174 19

The castle has rendering issues upon leaving the left door of blue spawn, but it may be a valve compile issue.
setpos -1846.382568 -3037.557861 -185.496185;setang -18.015881 62.360424 0.000000

You can build underneath the wood as you exit blue spawn to make people be permanently stuck/hide in the darkness.
setpos -1744.321045 -2287.571777 -227.355011

There's a stuck spot between bamboo and rocks on A.
setpos -2577.773193 -2181.839355 13.434128

You can stand on almost every single rock off the side in the water at A (that doesn't have hurt triggers) as well as a few places on the displacements against the wall.
setpos -4031.285645 -1553.276733 -283
setpos -4223.246582 -1119.137329 -323.437073

Displacement part you can stand on above A.
setpos -1555.992676 -1321.368530 432

Unclipped roof trim on A
setpos -3674.993652 -420.008484 94

Permstuck spot at B
setpos -63.690868 -2290.873535 34

Weirdly-clipped area that should probably not exist/have nobuild at B entrance
setpos -63.690868 -2290.873535 34

The nobuild in the water on B does not fully extend top the wall at the stairs. Can also build in the D water hallway and have some point coverage.
setpos 1871.330322 -1021.971924 -307

Few spots of the displacement wall on the side of B can be stood on.
setpos 2176.721680 -2671.475098 251
setpos 2118.916504 -1680.031250 261
setpos 2183.968750 -1195.968750 235

Roof corner part that isn't clipped off at B
setpos 188.031250 -940.031250 681

One of the rocks in the ground on point C is clipped off for better movement, while the other isn't.
setpos 2004.265503 2306.997803 -133

The func_nobuild does not extend into the water hallway at D, so if you go for a D push before capping A you can have water sentries helping you defend the point (after A is capped, this sentry viewpoint is blocked off). The trigger_hurt also feels really inconsistent (the one that exists before A is capped) since it's only at the surface.
setpos -253.924530 -58.374550 -387

Also almost every roof can be pixel-walked on, meaning if you approach the collision perpendicular to the collision you can walk on most roofs despite them being clipped off (this is a nightmare to fix!)

Let me know if you want clarification for anything,