Back story. Had car in airport parking for 2 weeks. While we were away battery went flat. They jump started and electrical issues have been a pain since. Can't use key fob for central locking, stereo stick controls no longer working. Have tried bsi reboot numerous times to no avail. Thursday night all rear lights were off but came back the next morning. Last night sidelights wouldn't go off at all. Had to disconnect battery overnight (followed disconnect procedure)
Had rac out today, and bless him he tried everything, and the only thing that would get the lights to turn off (other than the fuses that power them) was when he pulled green plug out of the bsi unit that's in the drivers footwell. Am so so annoyed as we've not ever had any issues before getting car back from the parking lot!
My friend David had exactly the same issue, his car was left at an airport for 3 weeks and wouldn't start upon return.
Prior to this though, the wipers and headlights were playing up a bit, sometimes they would work on their own - but after the battery died at the airport his car was immobilised.
Originally I assumed it was a dodgy comms unit ( indicators/wipers/stereo controls combo ) as the headlights were on constantly, but after swapping it over it hadn't fixed it.
I didn't originally check under the carpet as the car was bone dry, no damp, no water trails or anything - but after being 'prompted' to check David actually pulled out over 2 litres of water from under the carpet..!!
The connectors were damp and corroded, so the connector was removed and the wires soldered together and the car started - everything back to normal.
Good luck - hope you manage to fix it.
2003 2.2hdi estate - mine 1998 Volvo 940 auto estate - also mine 2019 Citroen C3 something - the wife's PP2000 user, can help with faults / diagnostics in the Bournemouth area.
