I know this topic has been covered so many times - but I can’t find the answer to my problem. 1998 SLK230 - Central locking wasn’t working but now is. However, I lock the car with the fob - all works as it should. Then after about 3 mins the alarm is activated. I took out the PSE, cleaned the connections, cleaned inside - there was evidence that water had been in - and re-assembled. Everything works as it should - but same 3 mins and the alarm goes off. Any ideas?