if (LMs == 1 && Ls == 1 && Cs == 1 && Rs == 1 && RMs == 1) {
pos = position;
MainS.write(pos);
position = 90;}
Two things:
1) If you want it to maintain the same position, don't change position to 90.
2) The servo will maintain position until you tell it otherwise.
If you eliminate the un-needed assignment (1):
if (LMs == 1 && Ls == 1 && Cs == 1 && Rs == 1 && RMs == 1) {
pos = position;
MainS.write(pos);}
If you then eliminate the un-needed write (2):
if (LMs == 1 && Ls == 1 && Cs == 1 && Rs == 1 && RMs == 1) { }
Now that the if-statement is empty you can eliminate that, too:
// In the case of (LMs == 1 && Ls == 1 && Cs == 1 && Rs == 1 && RMs == 1) we don't need to do anything.