This issue is unorthodox. It is based on testing and basic command block knowledge that after a command block had successfully executed a command; a redstone output can be released via comparator. 

During my testing on a command block machine; I used a repeating command block that has /kill @e[name=select-paint] in it and a Chain, conditional, needs redstone, command block that has /setblock ~ ~3 ~ redstone_block in it with a comparator as an output to another node of command blocks. There are three similar command block lines with the second one that has a repeater after the comparator. 

As I ran the first node, I realised that none of the comapartors detected an output from the successfully running command blocks. I can assure you that this worked fine before because as I restarted the world; the command blocks emmit the redstone outputs again! Unfortunately as I continue to run it,  they would not emmit redstone outputs reliably as I run it once, it will emmit, then second, does not, the third does, fourth does, fifth doesnt. The comparators are not reliably activating and are simply deviant to emmit the proper redstone output accurately.

I continued to test this issue and my conclusion is that the redstone comparators will have a 50% chance of activating after a 100% successfully executed command.

This is unfortunate to have since it took me hours upon hours to find out the issue. I hope Mojang developers can help fix this as swiftly as possible to give the command block nerds community of Minecraft a better and more reliable experience when fiddling with command coding.

My best regards.

Xbox Live name = CliveLeeYTM