Megan Fox and Machine Gun Kelly have a lot of "trust issues"

A source told PEOPLE: "The intensity is still there nearly four years into their relationship, but that's not necessarily healthy. There are still a ton of trust issues between them and it's very toxic. They can't stay away from each other and there's a lot of history there, but they also don't know how to be in a healthy relationship. They'll be totally fine, then days later get into a huge blowout fight and not talk for weeks, but then give in and be all lovey-dovey again."

The pair are said to be "living separately", with Megan in Malibu, California, while MGK - whose real name is Colson Baker - remains in their Encino mansion as they work on their romance.

Megan confirmed on the 'Call Her Daddy' podcast recently that reports about her and MGK calling off their engagement at some point are "accurate things that have occurred".

Host Alex Cooper said: "You got engaged and I think it got called off...how would you describe your relationship with MGK?"

And, Megan replied: "As of now I don't have a comment on the status of the relationship per se. What I can say [is] that [he's] what I refer to as being my 'twin soul.' There will always be a tether to him no matter what. I can't say for sure what the capacity will be, but I will always be connected to him somehow.

"Beyond that I'm not willing to explain, but all those things you said were accurate things that have occurred."