That's some bug in other mod, not in RA. Everything works fine for me. For example I can insert Jetpack Equipment from Jetpack mod into RA's MK3 armor. So it depends on the correct equipment implementation in other mod.
As I remember Krastorio has its own MK3 armor (or even MK4 too) - how do you play with such a mix? Maybe it's easier to switch off 'Enable Equipment' option in RA startup settings and use only Krastorio armor and equipment?