EasyTouch GFI breaker trips when it rains - narrowing down possibilities

[GmorningGunite]

Whenever it rains, a GFI breaker trips on my Pentair EasyTouch panel. It has all appearances of being a ground fault trip as it happens only during rain and regardless of any call for equipment operation. The breaker serves the pump, heater and Intellichem systems. Each system has its own disconnect, located at the outside wall. The trip occurs exclusively upon activation of the Filter Pump relay (enabling 'Pool' or 'Spa' via the app), as appears to power Intellichem/SWG and heater. I can still have the app run the pump at this time, but if I enable that Filter Pump circuit then it trips immediately.
Even if I pull all disconnects, the breaker still trips until many hours after rainfall has ended.
The breaker was replaced and resulted in no change. I've inspected all disconnects, whips, bushings etc in search of moisture. I also purchased a pump cover.
How can the breaker trip when all its disconnects are open? Could a short at a separate circuit (eg air blower motor capacitor shorting to ground), motorized valves, etc, somehow trip this circuit? Is there a way to narrow down the locations of the issue?
I've attached a picture of the panel wiring.
Any ideas would very much appreciated!

 

[ajw22]

Welcome to TFP.

Show us pics of the rest of your pool equipment and especially these disconnects you speak of.

 

[GmorningGunite]

Welcome to TFP.

Show us pics of the rest of your pool equipment and especially these disconnects you speak of.

Thanks!
Newish to pool ownership, so I appreciate the help! I've attached the equipment pics. The only thing not pictures is the air blower. It is a few feet away and fed by the same disconnect as the heater. I'd stuck a garbage bag over it just to rule out rainwater infiltration into the motor/housing. The pump is covered but is a Superflo VS.

 

[ajw22]

Where is your ET panel in relation to the two disconnects I see on the exterior wall?

 

[GmorningGunite]

Where is your ET panel in relation to the two disconnects I see on the exterior wall?

The panel is inside the wall, mounted on a backing board that's offset from the wall. Power connections are at the bottom, so no potential water intrusion there... Penetrations through-wall are directly to the disconnects using plastic raceways. Power runs to the disconnects are maybe 5-10 ft. There are a couple junction boxes--pictured--between the ET panel and disconnects where the Filter Pump circuits are divided. I opened them up, but no indication of moisture there.
Pic 20210822_170444 should show the 3 disconnects. The heater disconnect is partially hidden by the DE filter.