Lee assuming the pipe is now standing up vertical with the loop at the top it should not really leak.
Inside the box there is a series of plastic channels fixed to inner upper casing which act as a type of deflector to channel oil back so it's possible that one of these may be broke or has come u clipped but to check that the gearbox end casing will need to be removed.
The other possibility is that somewhere there is massive wear in the gear set this will generate heat which in turn will cause oil level to rise, but once again difficult to say unless inspected.
I had this problem with a quaife once on the track (especially on hot days) so this is what I did to resolve the issue.
Take the looped pipe and run it to a 3 way catch can (you can make one easily enough or buy one), run another pipe from one of the other ports back to the gearbox.
I drilled and tapped another fitting to the top front of gearbox casing so the oil that got pumped into the can simply drained back to the box. You will need to use the spare outlet to run an external breather filter at the top as the box needs to breathe.
Also with mine I ran a seperate oil cooler to try keep the temps down which all worked fine for a while
Then one day the box went bang and that was it
Was good whilst it lasted though lol
was mainly caused by a shoddy gearbox build with incorrect overly tight shim clearances which were putting way to much loading on gearset, this was generating a lot of heat which caused the oil level to rise.
Seriously though it's worth a try though lee