I will suggest a few things to strengthen the circuit. I saw many vehicle designs fail, junior engineers in tears. Since you have no I/O to GND it's ok for open circuit there I believe.
Understand the voltage transients on a vehicle electrical system, using ISO 7637-2: "Road vehicles — Electrical disturbances from conduction and coupling — Part 2: Electrical transient conduction along supply lines only"
For a 24V system expect vehicle switching transients (test pulse 3a) -200V and inductive load switching (test pulse 1) -450V to -600V spikes. 12V system is -150V and -75V to -100V respectively.
1N4148's good for 100PIV, a bit low. I suggest ES1 600V 1A fast-recovery (SMA) part might fit on your PCB pads.
For positive spikes +100V (12V) and +200V (24V) at 0.2usec at 10kHz (test pulse 3b).
This is the one that kills the 7805 or even a
MIC5281.
You must have a TVS and some series resistance on the input, to limit clamping current. Like 47R, this helps immensely.
Also 7805 can get hot on 28V, but I'm not sure total current including RF TX and LED.
FvM shows ISO 7637-2 (test pulse 5a) Load Dump but that is very difficult surge to tolerate, I don't bother designing for it unless I have lots of money.
If you are connecting to a trailer with ABS (SAE J560 connector), ABS braking high-voltage spikes can be present on the STOP lamp or AUX PWR line. I saw this on a trailer that kept blowing circuits up. Turning on gravel triggered the ABS.