Bosch SMS53E16GB/29 leaking

Hi i have a problem with a bosch SMS53E16GB/29 where i can’t find where the water came from that has leaked into the base and damaged the heat pump. The water that is in the base is a yellow colour and has left marks on the rim of the sump in the 6 o’clock position if you look from where the kick plate was before i removed it. This suggests to me that it has come from the door but the seal is fine. i have had all the panels off to check while running it but it doesn’t leak. I don’t want the new heat pump getting damaged after i fit it(which happened to me once before with a leaking water valve). The customer uses a clear rinse aid. The top spray arm was very stiff and not turning, can that cause this? Thanks for any help i appreciate it 🙂