Not a bug
BYOND Version:511
Operating System:Windows 10 Home
Web Browser:Firefox 56.0
Applies to:BYOND Pager
Status: Not a bug

This is not a bug. It may be an incorrect use of syntax or a limitation in the software. For further discussion on the matter, please consult the BYOND forums.
Descriptive Problem Summary:
Byond does not properly disable hardware acceleration.

Numbered Steps to Reproduce Problem:
Disable hardware acceleration in settings. Use Byond normally for a few days (frequently just takes a restart of the program but the higher reproduction chance the better).

Code Snippet (if applicable) to Reproduce Problem:

Expected Results:
Hardware Acceleration stays disabled in settings.

Actual Results:
Hardware Acceleration ends up reenabled.

Does the problem occur:
Every time? Or how often? Very frequently, no actual logs of tests, sorry.
In other games? It's a byond settings problem so of course.
In other user accounts? Not checked.
On other computers? Not checked.

When does the problem NOT occur? It's hit and miss, sometimes it happens, sometimes no.

Did the problem NOT occur in any earlier versions? If so, what was the last version that worked? I know for sure it's been around since the end of 510.

Workarounds: Don't have a graphics card that crashes if you use byond with hardware acceleration. Then the crashes this causes would be a nonissue.
This might be a won't-fix issue. I'm planning to get rid of software mode eventually anyway.

What sort of issues do you have when hardware acceleration is enabled? And what graphics card is it?
My graphics card is a cheap as fuck S24D590 on Radeon RX 460.

It's fine for most applications, but for 2D rendering it occasionally crashes my entire computer, turns the screen a solid colour, and the computer Reset button doesn't work. Nor does power. I have to flick the supply directly.

Byond triggers this issue, but it can happen in any 2D game.
Are you sure you're running the latest/correct drivers? Is your system able to cool itself properly?

Those sound like either driver issues or overheating issues.
I check and update the driver every time it happens, and sometimes it happens mere minutes after cold-starting my computer and getting into a game, so overheating is not likely an issue.

It's just a trash card.
I know ss13 as well as some other games do a thing to force hardware mode on because the darkness layer doesn't show up in software mode so people could use that to see in the dark and cheat.
In response to MrStonedOne
I suspect this is what's happening, since BYOND has no code that should force-reenable hardware acceleration. I'm gonna close this issue.

KFive, it sounds like there's something seriously wrong with your card or its drivers. I would strongly recommend replacing it.
Lummox JR resolved issue (Not a bug)