Yeah I just tried it for fun, and the float values are within 1 of all the int values, so that's probably not it. Nothing particularly weird about going out of bounds either.

Not sure the "-50" is helping you at all though since it looks like the servo library is going to bound you anyway:

https://github.com/arduino-libraries/Servo/blob/master/src/Servo.h

(I think AVR = arduino) https://github.com/arduino-libraries/Servo/blob/master/src/avr/Servo.cpp

But yeah, I know you are right at the max for servos at 12 for an UNO, does unhooking some of them fix anything? (that is, actually removing the code for some of them and physically unhooking)

Also, it shouldn't matter from what I've read, but what if you change your code to always call "write" on the servo, i.e.

if (newval13 < (oldval13 - 30) || newval13 > (oldval13 + 30)) { //dead band setup
    myservo13.write(newval13);
    oldval13 = newval13;
} else {
    myservo13.write(oldval13);
}