Bugs afflict the player's Navi during network duel and generally has a negative effect. When the player's Navi is affected by a bug, their emotion window will flicker.
They can be caused in the following ways:
- A NaviCust part is placed in a way such that it does not follow NaviCust part placement rules.
- A mod card with negative effects is installed (Japanese version only).
- The Navi is hit by a chip or program advance (e.g.
MoonBld, 
ElcPuls3, 
BugBomb, 
DestPuls) that causes a certain bug.
Movement Bug
TODO
Custom Bug
TODO
Panel Bug
TODO
Encounter Bug
TODO
Result Bug
TODO
Buster Bug
TODO
Disabled
The disabled bug causes the bugged support program (i.e. Rush, Beat, or Tango) to have no effect.
Battle HP Bug
The Battle HP Bug causes MegaMan's HP to steadily drain during the battle. Depending on how many bugs you have through the Navi Customizer (up to 3) is which level it starts with.
The Battle HP Bug drain goes as followed:
- Level 1: Drops 1 every 40 frames. Starts with this if have 1 HP Bug.
- Level 2: Drops 1 every 35 frames. Starts with this if have 2 HP Bugs.
- Level 3: Drops 1 every 30 frames. Starts with this if have 3 HP Bugs.
- Level 4: Drops 1 every 25 frames.
- Level 5: Drops 1 every 20 frames.
- Level 6: Drops 1 every 15 frames.
- Level 7: Drops 1 every 10 frames.
Notes
- HP Bug level can be increased by Damage HP Bug or by the special properties of certain attacks, such as Erase Tail Arrow or ElcPuls3.
- Using
BugFix will remove all levels of HP Bug regardless of their source.
Damage HP Bug
The Damage HP Bug increases MegaMan's Battle HP Bug by 1 level when hit by a damaging attack without having Super Armor (causing him to flinch) or a damaging attack that inflicts Drag, such as or 
ElcPuls2.
Custom HP Bug
TODO
Custom Damage Bug
The custom damage bug causes a set amount of damage to be inflicted when entering the custom screen. It can only be caused by use of Patch Cards.
Color Bug
TODO