There's a bug where the customnpcs from the customnpcs mod by Noppes doesn't do any of their scripted behaviour if I have both the customnpc mod and DS (I tried with every version combo of DS, fanasticlib and customnpcs for 1.12.2)

Maybe you can take the entities into the "S:"Entity-Specific Full Bypass" <" list and check it again.
Then CNPC will never react to DS but maybe your scripts will work.

Don't forget to close the tickets afterwords.

I was on a years-long hiatus when this was posted, and I assume you don't care at this point, but just in case this helps anyone...

It's been a long time (years!), but if I remember right, CNPCs...NEED TO SEE YOU TO TALK TO YOU!
In other words, IF THEY CAN'T SEE YOU, THEY CAN'T TALK TO YOU!

This very likely also applies to the check CNPCs is doing for running your script (I'm assuming this script is either conversational, combat/flee stuff, or in some other way requires observation of the player or other entities).

If you think about it that way, all you need to do is make sure the CNPC can actually see you (probably). If you're in creative mode, they probably can't, unless you changed the setting for that in DS so that creative players aren't invisible.

Pretty sure that is the solution, but if someone else still has this issue, comment and I can re-open it.