Can a mirena fail?

[Localher0]

DD had a mirena inserted Dec 21 and it worked wonders for her dreadful periods. After the first few weeks of spotting her periods stopped - unfortunately her acne got worse and she eventually started spironolactone which also had a positive effect after a few months.
In November 22 (11months later) she suddenly started having painful periods again and her acne has returned with a vengeance. (She also had her tonsils out in October but I think this is just a coincidence)
Could it be that the mirena has failed? Does this happen?

Can she feel the threads? Is the coil still there?

Yes it's still there and in place. She was vomiting on Thursday morning so rang gp and was advised to go to local sexual health clinic to check its position. They thought she could have an ovarian cyst so she was scanned yesterday. All normal and in place. After 7 hours at the Gynae clinic they basically said they don't know what's causing pain/bleeding so told us to get a gynae referral (isn't that what they're there for?).
I asked if mirena could fail - they said no. But I'm very confused why her periods would have stopped for 11 months and then restarted. I'd expect spotting to begin with then bleeding to settle. Not the other way round. 🤷‍♀️

In fairness to the sexual health clinic their speciality is not gynaecology so they are right in that a gynae referral is needed. The problem is at this time in the UK (I presume you are a uk resident) waiting lists for gynaecology in many areas are miles long. If it is possible for her to see a gynae as a private patient for an initial consultation I would go down this route.

She needs a diagnosis first and foremost. Treating the symptoms is only part of the issue because the cause needs to be established too. Has anyone ever mentioned endometriosis to her re the period pain, I suggest that as endometriosis is a common cause of ongoing and or severe period pain.

Her acne could well have an underlying hormonal cause and could well stem from she possibly having PCOS (poly cystic ovarian syndrome). This could also account for her periods restarting after an 11 month gap, it does cause irregular periods to arise. It is certainly in her interest to establish exactly why her periods are as irregular and painful as they are and she will need to be persistent in order to get answers. I would suggest she keeps a daily pain and symptom diary noting everything if she does not already do this as this will give a gynae clues.

Thanks @AttilaTheMeerkat I'm concerned about endometriosis too. I asked at the clinic and they said it would need a laparoscopy to investigate so again to see a specialist. Luckily we had already made an appointment with the doctor who inserted the mirena as the bleeding / acne has been grumbling for a while. So fortunately we will see her this week. (We have BUPA through work). Hopefully she can do further investigations and at least we can take the results of the blood tests and scan report with us so that should speed things up.
She just feels so rotten and is absolutely tired out as well as being in pain.