When one servo moves, all the others rattle. How to fix?

Question

Arduino

There is such a device

anduino nano + bluetooth module + 4 servos (sg90 9g, 5dcv).
PIN's
servo = d2, d3, d4, d5
bluetooth = d10, d11
Via bluetooth you send a message to all servos to turn to a certain angle.
Many times per second. And when one moves, all the others tremble.
Algorithm:
1. Arduino receives 4 bytes.
2. If the angle should change from the current one, then servo write and so on.
3. All
Mounting: soldered. Contacts checked all reliable. KZ is not. Anduino and bluetooth are powered by USB, servos from another source. Common (earth/minus) combined.
Action taken :
- changed the power supply to a 5v block from the phone, with an output of up to two amperes. Batteries Lithium Ion. Power supply from a personal computer. - no change.
- paused between commands for more than a second - no change.
- Soldered capacitors to each servo - no change.
- connected +Vin servo to the source in parallel and in series - no change.
- left only one servo, and sent a command to the contact without a servo to turn around the corner. A connected but not commanded servo also rattles.
- changed arduino to others, also changed servos.
HZ in short, how to decide?
!! The problem is not that the servos are shaking on their own, but that when you send a command to one servo, then all the others start to shake. !!

Answer 1

1. You need to download the servo check sketch from the Arduino tests, correct it for angle control from the comport and check all your servos. There are faulty servos that shake. They don't have good electronics.
2. Take an oscilloscope and each channel that is weird to check the constancy of the pulse width. And to understand why such miracles can be: rc-chains or jambs in the code.

Answer 2

No interference can be induced in the node?

Answer 3

What does "jiggle" mean?