Help with a conundrum

[DG&H_MRRinN]

Hello, I am new to the site.
I have been puttering around with various little projects that creating things.

But Im in a little pickle of confusion atm.
I am building a project where I am using an Arduino Mega, a L298 R3 motor shield. an ESP-01S Wireless WiFi Development board, and a LCD 16x2 screen.

So, I wanted to tidy things up, and make it a bit neater for myself, and I grabbed a PCB board to try and mount the WiFi and LCD too.
I put a header for the WiFi board to seat into, and pins for the board to seat into the Motor shield. connected up the 3.3V to the appropriate pins on the headers, Grounds to common Ground, and 5V to the LCD board. I then have 2 jumper wires going from the LCD board to pins 20/21. And 2 jumper wires going from the header to pins 18/19 for the WiFi board.

The LCD, no issues. The problem I am having is, when I plug the WiFi board into the headers, the WiFi board doesn't work. But, through hours of testing, I have found that when I connect 10cm jumper wires to the WiFi board, and the header I installed, (1 wire for each of the 5 pins in use), the WiFi board works like a charm! Any ideas on things to look for that might be causing this issue? Thanks in advance for checking out my problem, and offering advice on how to fix.

 

[rjenkinsgb]

It could be any combination of antenna shielding effects and RF noise from other components desensing / swamping the WiFi receiver.

Desensitization (telecommunications) - Wikipedia

en.wikipedia.org

eg. WiFi in such as laptops generally has the antennas as far as possible from the CPU/logic board, on cables through the casing.

A module like that which has a tiny and inefficient antenna built in is likely very! sensitive to noise and positioning.

 

[DG&H_MRRinN]

Thank you for your assistance. I kept thinking it was something physical that I had done wrong. I guess I just need to redesign this board.....

Do you think by moving the headers from where they are now, to the far left, (the part that overhangs) would be far enough away to prevent this problem?

Again, thank you everyone for looking at this, and to RJ, I would never have thought about that sort of interference.

 

[rjenkinsgb]

Do you think by moving the headers from where they are now, to the far left, (the part that overhangs) would be far enough away to prevent this problem?

It's very much trial and error; with all the loose wiring plus "fast" signals on the boards, there will be a lot of stray RF around..