There is a bug in the combat selection of pvp when there are two players on top of each other. Sometime your game will auto select the opponent that you are not able to fight because their combat level lies outside of the danger level from you combat level. There is no way or combination of attacks to select the character you can attack that does lie within the bounds. Here is an example to clarify:
GarionTheFirst - cl 135
a6070160701 - cl 127
hell_master - cl 54
Danger level: 40+
Both miners are mining the same redhodium spot. Attacker attempts to attack the miners but game only allows hell_master to be selected with right click and when shift+click or shift+walk is used it says danger level is too low because game selects hell_master as target. Effectively this bug could be used by low level players to shield higher level players in nml. A possible fix is to allow other options when right clicking so that the other player might be accessed.
Please ask for more info if there is confusion about what the bug is