Van central locking issue

[Benjimia1]

Hi my berlingo van doors was open one night as I was unloading my van, all of a sudden the horn started beeping but solid for 20 seconds at least, I tried locking and unlocking but this didn’t stop the noise, so I pulled the horn fuse as it kept doing this every 30 minutes and was getting really annoying, since pulling the fuse the horn has stopped working but it doesn’t continuously go off randomly, but now my key fob only works if I open the doors manually and get in the van, so I can lock the van with the fob but as soon as I walk away from the van it won’t re open and the fob doesn’t work, iv changed the fob battery and done the reset system in the ignition, could it be a bad car battery? Any help please

[wheeler]

What year is the van?
Has it recently had any work done to it?
Does the van have the original radio fitted to it or an aftermarket one?