The Masked Singer

This season of "The Masked Singer" has been plagued with security issues ... and with the season finale approaching, the team is doing everything it can to keep a lid on the show's best-kept secrets.

Our sources say fans and paparazzi have been outside the studio, trying to snap pics through cracks in the fence -- some have even climbed on top of cars to get shots over the barricade.

We're told the studio has seen an increased swarm of people at the entry gate, and it's creating headaches for producers as they try to deal with everyone trying to sneak a peek.

To avoid leaks, the set designers stepped up in a big way ... they worked closely with the 'MS' security team and used set pieces from past performances to build a makeshift barricade outside the studio!

Sounds like lugging giant sets outside and repurposing them as a blockade was an exhausting ordeal, but ended up being worth the effort. Producers were worried that one open sliver would give photogs the shots they were after ... but luckily no pics made it to the light of day.

The most dramatic moment from this season of "The Masked Singer" has finally played out ... as Rudy Giuliani was revealed as a contestant, causing one judge to walk off set.

The whole thing went down on the FOX singing contest Wednesday night as the disgraced politician and former right-hand-man of Trump was revealed as The Jack in the Box. Giuliani got the boot after this week's performance of "Bad to The Bone."

While he's performing the song, you see a clearly pissed-off judge, Ken Jeong, say "I'm done" before walking off the set.

It was back in February when it was reported both Ken and judge Robin Thicke walked off in disgust after Giuliani's reveal ... but that didn't appear to be the case Wednesday, with only Ken leaving.

For the first time in "The Masked Singer" history, there's a team working behind the scenes to help operate one contestant's costume ... resulting in a massive fail if the slightest thing goes awry.

Here's the deal -- the Space Bunny's signature shifty eyes aren't controlled by the mystery celeb inside the costume ... instead being operated by a producer backstage via a Nintendo-like controller.

We're told coordination is key ... the slightest change in the performer's routine could throw the entire thing off!

To make matters worse, the high-tech equipment inside the head hasn't had all of its kinks worked out yet ... there's a super loud buzzing sound inside the mask that's distracting for the performer -- something that could easily make them forget the words or choreography for their performance.

We're told the celeb in question has been a great sport so far ... producers gave them the costume because they felt they'd be able to roll with the punches and take on the challenge.

Let that be a clue -- this contestant is a bit of a risktaker, and is certainly not a diva.

The 'Masked Singer' might have a cursed trailer on their lot ... because one of the mobile celeb dressing rooms has a toilet that just won't seem to flush.

Here's the deal ... each contestant hangs out in their own StarWagon trailer during long days on set -- not unusual for Hollywood productions -- but one of the trailers is having serious issues with plumbing.

Our 'Masked Singer' sources tell us one of the contestant's trailers had a clogged toilet, and the celeb had their entourage make the embarrassing call to alert production. It's kinda the whole point of "having people."

Anyways, the crew unclogged the toilet -- we've all been there -- but a few days later, we're told the same trailer had another clog, and the celeb again got their person to call on the plunger posse, much to the celeb's chagrin.

For context, these StarWagon trailers are equipped with bathrooms roughly the size of an airplane lavatory. Hey, it's still better than a porta potty.

The 'Masked Singer' could've been a massive mess ... cause TMZ has learned, one of their biggest contestants almost dropped out 48 hours before filming this season!

Our 'Masked Singer' sources tell us, no contestant has ever threatened to quit so close to the start of the season before ... so everyone was caught off guard, and without a backup plan ... they were pretty much gonna be SOL.

Basically, execs of the show would have to completely revamp the entire season ... just before it was set to began. Luckily though, they were able to do some serious damage control ... and the show went on as planned.

We've learned there are a number of things that played a part in the contestant's initial decision, ranging from feeling ill-prepared to feeling overly restrained in the costume/mask.

We know what you're thinking ... but this wasn't a case of stage fright. We're told this particular contestant is no stranger to live performances on stage, but the giant costume completely threw them off.

These kinda "wardrobe malfunctions" aren't new to the folks at 'Masked.' As we previously reported, the complexity of the costumes has raised lots of concerns ... ya know like onstage wipeouts, safety of the contestants etc.

In this case, crisis was averted ... that is, after MS producers sent flowers to the performers and gave some much needed pep talks and praise. Turns out, the contestant ended up being a really strong performer and we're told they have the potential to win it all.