I am currently creating an escape room at my house by using a lot of castle magic. One obstacle I wanted to make was one that you have to step on magic pressure plates in the correct order or else nothing will happen. My plan is as follows. Btw to make it simpler to understand, I'm going to call the magic computers: Computer A and computer B.
The first magic pressure plate you would need to stand on added signal one to computer A and removed signal two from computers A and B and signal one from computer B. The next magic pressure plate that needed to be pressed would add signal two to computer A and remove signals one and two from computer B. Next magic pressure plate added signal one to Computer B and removed signal two from computer B. And the final magic pressure plate added signal two to computer B.
The logic behind this was if you for example pressed the magic pressure plate that was meant to be pressed second for the first one you pushed, eventually when you would press the magic pressure plate that was mean to be pushed first, it would remove the signal added from the first magic pressure plate you pressed (in the example provided, it would turn off signal two from computer A).
I finished building this, and it worked...well so did all the other combinations . I concluded after experimenting a little more, that the remove signal did not work in my case. I am almost 100% percent sure that this is a bug, but if its not and I'm doing it incorrectly, plz let me know how I can perform this correctly.
Try re-selecting every one of the spell targets involved. Even if they already appear to already be set correctly. And then test again.
I have found that moving, adding, or removing a magic item can sometimes cause "permanent" spell targeting problems with any like magic item in the area. So in your case, the wrong magic computer may now be targeted by a spell even if you had previously targeted the correct magic computer. And it may even appear to be targeted correctly (with arrows pointing to it and flashing) but still it never gets triggered (until you re-select the spell target).
Looking more closely at the problem... One way to solve it is by adding a third magic computer. The third magic computer (I'm calling it the "Master" computer below) will make the ultimate decision to open your escape room, based on input from the other two magic computers.
Here is logic for three magic computers:
In the example below,
P1-P4 are pressure plates 1-4
A is magic computer A
B is magic computer B
M is the "master" magic computer
+ = add signal
- = remove signal
Spells cast by pressure plates to add or remove magic computer signals:
Thank you so much! I really appreciate your awesome help ! Only one combination works and I cannot wait to use this logic to make other challenges! If you have any ideas on challenges I should do, please let me know, as I am running out of ideas!
. I concluded after experimenting a little more, that the remove signal did not work in my case. I am almost 100% percent sure that this is a bug, but if its not and I'm doing it incorrectly, plz let me know how I can perform this correctly.
I have thoroughly tested this logic in my castle laboratory, and it works. 
! Only one combination works and I cannot wait to use this logic to make other challenges! If you have any ideas on challenges I should do, please let me know, as I am running out of ideas!