As one of the developers on Periodic Madness (I just do functionality things, don't ask me anything about the mod), we had someone come in who had an issue with this mod.

In the process, we discovered that your Squeak Through replication is a data stage process... This is fundamentally not where you should be doing things. That should be a data-updates like the original Squeak Through or a data-final-fixes like Squeak Through 2

Still isn't compatible with PM with that fixed, but I'm chalking that up to the difference in complexity (your 17 lines vs the 155 of Squeak Through 2).
I also personally believe a modpack is better than packaging the mod concepts together, but that's separate.

Could you maybe print out the stack trace? I personally did not ever heard of that mod, so maybe i miscalculated how to proccess mod compatibility.

And to answer your question about ST 2 and my implementation
It's simple as that. The original mod basically make a lot of customization (which evaluates a lot of entities, which are need to be handled differently) to the entities that are processed. And for some reason he is making custom collision mask for some reason (which is not needed at all)

My function just takes the collision box, that is already in the game and then shrink it. It does not have mod compatibility from the scratch because of that.

But still it does not mean, it should not start with another mod.

I have rewritten the function on my end and added your mod as load after. My mod now should fully work with yours ;)