Association Line disapper

Hi guys:

I create custom element base on this example yesterday and I find problem now. I can connect custome element with sequence flow . The problem was once I move either one of these two elements, the sequence flow will be lost.
Can someone tell me why?? By the way, add direction to custom connections is too complicate!

exist 2

Please describe, what behavior you’re trying to achieve. What changes have you made to example?

What do you mean by

It’s easier to help you if you describe a problem in clear terms instead of saying it’s too complicated.

pretty much similar with this problem, but they did not solve.

Here is part of my code 3

So you want to connect your custom elements using sequence flows? What’s the use case of that?