One train - the 1808 off London Bridge [LBG], as you mention, IIRC - was terminated at Oxted [OXT] due to door problems. Staff were unable to resolve the issue. I'm not entirely sure what the issue at Upper Warlingham is, but it appears to be separate on JourneyCheck, but not on NRE or according to Southern.
I was at East Croydon when the problems began and there were certainly a number of trains delayed and, at that stage, were simply awaiting signal clearance whilst the fault was expected to have been being dealt with.
In addition to the advice on NRE, which I have posted below for forum users' convenience, I would strongly advise that if TOCs permit it, passengers should travel via Redhill if they require a service to Edenbridge. Services will have sufficient room to accommodate a decent number of additional passengers.
No trains between East Croydon and Oxted until further notice
A broken down train is causing disruption at Upper Warlingham.
Because of this, the following alterations will apply until further notice:
- Trains are currently unable to run between East Croydon and Oxted
- Buses are running between Purley and Oxted and between Three Bridges and East Grinstead
- Buses are running between Haywards Heath and Uckfield and between Buxted and Crowborough