Problem with OLED Display Voltages (String Command) using transmitter and Receiver

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18

Could you make the buffer larger, for example 20 or 40 bytes.
The width of 5 for dtostrf() is a minimal width.
See here: https://www.nongnu.org/avr-libc/user-manual/group__avr__stdlib.html
and search for the word "minimum".