Renting: Landlord escalating to Kronofogden & Hyresnämnden - anyone experienced this?

Hej,

I'm a foreign national renting in Stockholm, looking for other people's real experiences before I take this further. Got a rental situation that was stable, but kinda turned messy & escalating.

Background:

• Renting the same apartment (a new-build) since 2022: I'm the first and only tenant it's ever had. Landlord has said openly it was bought as an investment property.
• Contract (förstahandskontrakt: first-hand contract, hyresavtal på obestämd tid/tillsvidareavtal — indefinite-term agreement) is signed directly with the landlord, who is based in Stockholm at a different address.
• Account has always been in good standing — no issues on that front at all.
• Since Jan this year, I've been receiving notices not from my actual contracted landlord, but from someone who appears to be his brother, based in the US, corresponding as if he is the landlord, the dynamic between the two of them is unclear and honestly confusing.
• The notices have made a series of shifting, spurious claims: first alleging arrears that don't exist, then that I must move out within a month due to contract terms that aren't accurate, then that new tenants were already booked in.
• I contacted Hyresgästföreningen (the Swedish tenants' union) and was advised I have besittningsskydd (security of tenure) and don't need to take any action.
• A later notice invoked privatuthyrningslagen (the law on renting out one's own home, which removes besittningsskydd), claiming personal use, the brother said he intended to return to Sweden and wanted the apartment back for that reason.
• However, checking the listing on Qasa showed the flat had actually been re-advertised for rent at a higher price, suggesting the "personal use" claim was pretext.
• Numerous further deadlines were issued; I was advised I didn't need to act on any of them. The brother has now made an application through Kronofogden (the enforcement authority) for avhysning (eviction), which I intend to contest.
• I expect this will end up going to Hyresnämnden (the Rental Tribunal).

What I'm asking: Has anyone dealt with a similar situation, a landlord (or someone acting as one) using shifting/spurious grounds and a personal-use claim to try to remove a tenant with besittningsskydd? What's your experience of a dispute escalating to Kronofogden and/or Hyresnämnden, and any advice for someone in my position? Mainly just after some stability at this point, not looking to be pressured into an unnecessary move if I'm legally entitled to stay.