While I don't have a front bed end, you have to figure out exactly where the leak is from, otherwise your just poking around in the dark.
Make sure the area is clean and dry then with a cloth that has a very,very light covering of cooking oil ( a chux with a quick spray of oil) wipe over the area where it seals, you only need a smear, then give the area a sprinkle of talc powder enough so you can see it, it should stick to the smeared oil. Run a blue chalk stick over the rubber seal and close the lid, open up and you should have a nice unbroken blue line where the seal is against the body, if not thats a possible leak area...............But wait, don't touch anything, your not finished......close the lid after marking the bad spots then hose down the outside, just as if it's raining at 80kph, open up and have a look, leaks should show up as snail trails in the talc powder.
Using builders line marking powder which is coloured is better.
There's probably other ways to check but this is an old and easy way.
Failing that gaffer tape is only $4 a roll.