Even after upgrading both RMX-OS and the Blizzcontroller and the Blizz-ABS to the MAX, its still there.
One player enters, and the enemies are active, a second player enters and it looks like the enemies are updating one way on the first player's screen, and another way on the second player's screen, however server only responds to enemeis being hit on the player 1's screen... (ie: if player2 walks up to an enemy that is in the upper right corner of the map on player1's screen, but isn't on player2's screen, player2 can still hit said "invisible" ghosty, and be hit back) if player1 at any point decides to leave the map, all enemies lose activity and just sit there. If player1 comes back, enemies are still dead rocks sitting on the field. All players seem to need to leave the field and come back in order for it to be 'correct'.
current versions (up-to-date, right?)
rmxos=1.13
blizzabs=2.79
blizzcon=1.02
And after a bit of tinkering with the idea of killing enemies on one screen with the other player instead, I gave up and decided to leave the map and it popped an error, something about undefined methods for 'x' in the Game_Event script. Hmm.

Also, I discovered that the err, Exp_Factor script, using enemy exp to indicate levels and making all EXP fixed EXP when gained, well, I noticed while I was killing monsters like stated above, that both players on the map were gaining EXP from this, even though they weren't in a party. Sticking between ABS and ABS-Controller resolved this issue. derr >.<
And as stated in prior posting, the exact error in regard to the has_key? thing:
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Client 2 (0002) at TIME UTC has caused an error:
undefined method `has_key?' for nil:NilClass
./Extensions/BlizzABS-Controller.rb:136:in `client_update'
./Data/Client.rb:43:in `block in handle'
./Data/Client.rb:43:in `each_value'
./Data/Client.rb:43:in `handle'
./Data/Server.rb:258:in `block in run'
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Yep. Sorry to complain a whole lot. I just want it to work, and even though it seems to work for everyone else, these issues came up when rmxos was like only 1.02 version or whatever, and its still coming up. Perhaps it means >I'M< doing something wrong?
--J