It appears as though the bug mentioned in the main post has been fixed with a couple of tries; if anyone happens to spot a bug, or spot the known bug occur again, post here.
Now, to explain a little what was going on to anyone interested:
How this script works is that when a player goes in-game, it saves the name and time they went ingame to a file (Sy_IsIngame.txt). When a player is seen leaving, the script takes the time from the file into a variable, and deletes the saved line from the file that contains names of players ingame at the time, and the times they joined.
What turned into a problem was that when too many logouts occur at once, the script failed to remove the name from the file, so the old time they joined was still saved in the file. So, when the same player joins again, the new time is saved after the old login time; when they disconnect, the script looks for the first line, and takes the time in that line, and the result becomes some long play time (of like 1day 3hrs, so and so).
The script now saves every login to the top of the file, and as an additional check just to be sure, it will clear the file (Sy_IsIngame.txt) whenever the server is seen empty.
I'll be working on Paranoid's suggestion of logging total time a player has spent ingame, and if I find time (and ways to have it done through the activity system), it'll come soon.
I just felt like writing something long and neat, to be honest! lol
