Descriptive Problem Summary:
When a turf is in another turf's vis contents, and has a part of its appearance changed while a client is not in the first turf's view, that change will only show on the original turf once the vis_loc'd turf is in view.

Numbered Steps to Reproduce Problem:
#1 insert turf A into turf B's vis contents
#2 move out of range of both turf A and B (I believe this is the maptick window, or view + 2)
#3 update turf A's appearance (here I am changing alpha, I've seen it happen with overlays/underlays too)
#4 move back in range of turf A, see no change
#5 move in range of turf B, move back to turf A
#6 see change?

Code Snippet (if applicable) to Reproduce Problem:
https://github.com/LemonInTheDark/basic-test-project/tree/ vis-fuck

Expected Results:
turf A will update as soon as it enters view

Actual Results:
turf A fails to update until turf B is viewed
See https://file.house/CApo.mp4

Does the problem occur:
Every time? Or how often? All the time
In other games? Not sure, replicates on a bare testcase
In other user accounts? Not sure
On other computers? See above

When does the problem NOT occur?
Never? I thought it might have something to do with vis_flags but that doesn't appear? to effect it. It's strange.

Did the problem NOT occur in any earlier versions? If so, what was the last version that worked? (Visit http://www.byond.com/download/build to download old versions for testing.)
I'm not aware of this, if you want me to hunt it I totally can.

Workarounds:
N/A