Warrior General Games

http://glb2.warriorgeneral.com/game/replay/11521/2081271
CBs D. Jon Flanders and Kip Fuller run to the top edge of the field while letting 3 WR go deep

on several other plays i've seen the CBs just wander around on vacant real estate while not covering anybody.
http://glb2.warriorgeneral.com/game/replay/778/1109444
D. Jon Flanders runs to the bottom edge of the field where there is no one to cover instead of running with the WR into the end zone

http://glb2.warriorgeneral.com/game/replay/778/1109719
D. Jon Flanders and Bubba Singletary not covering anybody.

http://glb2.warriorgeneral.com/game/replay/6667/1074421
they both do the same thing on this play.

first one does look buggy

2 CBs run up to the top of the screen and just stand around not trying to cover anyone while 2 WRs run deep against 1 FS
http://glb2.warriorgeneral.com/game/replay/12079/2177403

2 CBs run to the bottom of the field instead of covering 2 WR who run right past them
http://glb2.warriorgeneral.com/game/replay/12467/2233672
does anybody think this is how real football players would react in a real game?

All four of those are cover 4 zone defenses, meaning the CB's are covering zones, not receivers. Technically they are not buggy. They are doing what the play diagrams tell them to do.

Any bugginess could easily be attributed to having man-oriented corners playing zone schemes. 95% of CB's created in GLB2 are man corners. Your DC is doing a disservice having them play zones.

The first one is the only one that looks odd, but mostly because of the stoppage on the MLB and FS in the middle.