Hi cocopops,
There is a pretty good chance that what is happening is that the “max particle in trail count” is too low as this takes priority over your “max trail count”. In other words if you are limited to 500 particles and a single trail of particles has 50 particles alone then once you hit 10 trails you can’t display any more even though you have your max trail count really high like 100 for example.
When this happens the particle system will compensate by moving left over particles from a dying trail (when the source dies) to a trail that is supposed to exist currently but can’t because the particle limit has been reached. The result is exactly what you described.
Here is a screen shot of the settings I described for reference.
Just increase this value and that should help. Also make sure that you have “Clip Source Segement” checked just in case.
let me know if that helps,
Ed