Thinking it is rather unlikley doesn't mean it didn't happen.
Of course, but we're in a situation here where the company might decide eventually to prosecute the OP, so if they have a defence it is important to explore what those are, and whether a court might believe them.
Being allowed through at Marylebone once might just be one of those things, but being claiming to be allowed through, ticketless, routinely, raises an eyebrow.
Not only do we have loads of posters here who use the station regularly and know that behaviour is unusual, we also know, from years of posts here, that Marylebone's gateline is extremely strict and very intolerant of ticketless travel.
If I was investigating the OP and knew they had claimed they had got through Chiltern's gateline many times by sheer force of charm, I would be pulling their purchase history, as well as requesting their Oyster or contactless payment records on the TfL system. The OP might wish to consider if this is something they would feel comfortable with happening.