strange problem with 4 ESC's and 4 motors

[Robin2]

There is a simple way to deal with this, or to prove definitely there is a problem.

Focus on a single ESC and the motor it is connected to and stick with that combination.

Write a short sketch that makes that motor start and stop. Does it always start and stop with the same numbers of microseconds? For example if it sometimes starts with (say) 1501 microseconds and always starts with 1507 microseconds then 1507 is the appropriate number.

Try the same thing with each of the ESCs with its motor (and don't mix motors and ESCs later).

Can you identify the number of microseconds that is required to start each motor (you will probably have a different number for each motor).

When you have established reliable starting numbers for each ESC and its motor then try all 4 in the same sketch.

If you can't find a number that reliably starts each motor let us know.

...R

[Cheyenne]

Its random- thats why I can use offsets....
I.e sometimes motor 1 starts at 1050 and motors 2,3,4 starts at 1051, sometimes motor 1,2 starts at 1051 and motors 3,4 starts itself after 2 seconds....randomly

Ok, then it isn't a problem in my opinion. A difference of 1 microsecond is very little.  A system  ESC -  brushless motor I think it hasn't more precission at start velocity but I think  it is enought.