Keyframing Force Fields seems to disfunction

Hey Guys,
first post, so sorry for mistakes.
I am using the latest Blener build and have a pretty complex model.

I got 2 different particle systems which shall react to two different force fields: both: “Force” (pushing all particles away from its center).

So if I simulate the particles without any force fields applied they react different when i simulate them with a force field…triggered to start later (at frame 100 for example).

So the force field(s) are 0 from frame 1-100 and 1 from frame 101-105. Keyframed by clicking on the strenght parameter and then press “i”. But the particles act like the force is always applied - from the very beginning. So the keyframing seems not to work properly.

Someone can help or witnessed something similar. (The strange thing is when i create a new model and do the same thing it works just perfect - the force field starts to work when the frame is reached)

Thanks in advance !

It should work. I have done this task before. Maybe you need to rebake your particle cache? (i.e. looking at old data) Also set your cache step to 1, it defaults to 10.
If you can post your BLEND file, simplified, I’ll take a look.