More info will be needed.... Is this where the campground electric pedestal panel is located...
I would look at the pedestal connection for sines of arcing... The 30A side really get used more than the 50A side...
Your visible socket before plugging in may look like this...
Google image
If you plug your shore power cable into this socket it will start arcing and end up looking like this...
Google image
You will have to replace a plug if it looks like this...
What I do sometimes if I find the 30A side bad like shown above will plug into the 50A side using a 50A to 30A long power adapter… This only taps into one side of the 50A service and will be safe to use on your 30A Trailer...
Google Image...
Reading up on 'NO SHOCK ZONE' online can give you a lot of good info for things like this happening...
Hope this helps... I'm just guessing on where the arcing is coming from...
Roy Ken