i've experienced this, i refer to as 'bleed-thru'...happened a few times, but more notably this past time, i have a basic script, the first thing it would do was SkipTime 12 on a empty playground testing mission i use to turn to night (faster than changing the editor options every time). When testing my scripts i am constantly hitting the "restart", and restarting. One screw up i had done (for got a semi-colon), and subsequently fixed, suddenly caused the SkipTime not to work, but the rest of the script would continue -exactly- as written, no errors, etc. I would have to exit the game to get it to run properly again. Its like it would be ignored (or the game hickuped, and believed it was -already- night, and i was skiptiming back to day?)
It is hard to describe, but when you feel the effects, its clear, something is not being cleaned up or reset to zero every time preview or restart is hit.
-----UPDATE:
because it feels relevant, even though not specifically a scripting error, its representative of the bleed-over i was describing. I just added a intro.paa to my description.ext, upon mission restart from within the editor, the paa displays correctly, but a few seconds in it reverts to the previous default mission image. Subsequent restarts same thing. It appears for each image shown, the blue progress bar does one full load.
Ok, gets better:
exiting back to the editor, clicking preview again has the same exact effect. BUT, click save once, when click preview this final time, the proper intro.paa is shown through both full progress bar loads.
This to me means that part of the mission is always being loaded from memory, even though other parts freshly loaded. IMHO