Just about everything I try mixes well with KCKT but it just may be my hair. The only "bad" result I got was with Eco styler olive oil. It had some flakes but they kind of scrunched out.
Today I tried KCKT, JCRR, with a tiny bit of LALSG and had amazing hair. It felt light and my curls popped. One of my best hair days ever.
I have also had good results with KCKT, then re:coil, with a gel on top, usually LALSG, but also Pantene curl sculpting.
Another success is KCKT, and KCCC but this took awhile to work out as KCCC can be a brat at times.
Also, some other product in your routine could be an issue besides the gel. Your rinse out may have not been rinsed out all the way which could have mixed badly with KCKT.
Experimentation is key. HTH
3a/3b, Fine Hair, Low porosity, Medium Density
Poo- CHS Treatment Shampoo
Low-poo- Devacurl Low Poo
RO- Devacurl One Condition
Leave-In- KCKT/Curl Junkie Smoothing Lotion