Descriptive Problem Summary:
There are two issues at work. Here is some background:

In SS13, a "beam" is assembled with a line of objects between two points, arranged using mathematics to create the illusion of an unbroken object.

Issue 1. In any version of 515, starting from 515.1590 up to and including 515.1602, these "beams" are not behaving correctly and are being transformed incorrectly.

Issue 2. Occasionally, usually the first time you run the code after changing BYOND version, the icons will "flick" between two appearences, despite no procs running on them and them not being edited in any way. This part of the bug is secondary and I am unable to offer any sort of explanation or solid reproduction steps to this part.
Image examples of the two "states" it flicks between are on BYOND discord: https://cdn.discordapp.com/attachments/725458744711839873/ 1083463633838804992/image.png and https://cdn.discordapp.com/attachments/725458744711839873/ 1083463691757965383/image.png

Numbered Steps to Reproduce Problem:
Create a beam. Move around. It remains broken no matter the angle. It sometimes just changes in appearence despite nothing being changed about it.

Code Snippet (if applicable) to Reproduce Problem:
Test project on BYOND discord, at https://cdn.discordapp.com/attachments/725458744711839873/ 1083490569742975077/Test_src.zip

Expected Results:
An unbroken appearence.

Actual Results:
The beams appear broken.

Does the problem occur:
Every time? Or how often? Every time.
In other games? Yes, test case created and happens in multiple SS13 codebases.
In other user accounts? N/A
On other computers? N/A

When does the problem NOT occur? It always occurs in 515, from 1590 to 1602

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.)
514.1589

Workarounds:
Use an old byond version