First I'm sorry to post this in the general discussion, but I've already posted three times a similar topic in the bugs section that was moved in the closed bugs. The problem is related to creating objects with physic behavior on the fly. As seen in this topic https://www.scirra.com/forum/physics-error-and-crash_t150137, other people encounter the same bug, and it seems to be not linked to how many objects you create even though the bug occurs more often with many objects created.
After testing, and reading others comments and experiences, I'm pretty sure it's not the "way" asm.js is programmed, but a memory leak.
So I posted here because Ashley closed the topic each time with no more explanation and we can't discuss any more about and maybe find a solution.
If someone is interested, we can go further together. It's a big issue for me as I'm working on a commercial project and at the moment I'm stuck on this (it crashes the program).
Thank you all for your time.