Comparator doesn't activate more than one command

As seen in the picture, there're two command blocks attached to a fill command, both with a comparator that activates two other command blocks and another one after the repeater. The command blocks attached to the fill command are testfor commands and check for a player looking at the sky (rx=-90) in two different positions. Now, the strange issue is that it seems that, of the two command blocks attached to the comparator, only one is activated: in fact, if I remove the blocks above the quartz_block, the remaining commands activate, but if I put back the commands I've previously removed, only these ones will execute. I've tried a lot of different dispositions, but every time only one command is activated. To add to the odd situation, activating the not-working commands manually (with buttons, redstone_block...), they will execute, while the comparator still seems to activate only one. Any attempt to fix it failed.