Hello board members

I require your experience and advice regarding a used Bosch Compact Dishwasher model SKS51E18EU bought recently.

The previous owner of 5 years mentioned an issue that it doesn’t drain at the end of the program, so restarting a new program clears this issue.

After good results for 7-8 cycles its behavior changed.. The ordinary program sequence begins: Drainage > Emptying all water in the system > and then the inlet pump starts taking in water, after ~15 seconds of water going in, the "check water" indicator turns on, and the program ends with a long drainage. total of 3 minutes since program execution.

I checked:

• Different configurations of the in/out tubes in different angles while running
• The inlet filter - was clean
• Drainage filter + unscrewed some piece to reach the cog-wheel of the pump making sure there are no obstructions

After looking online I found that for similar cases some concluded this might be the inlet valve, before ordering a replacement I need certainty that this is the solution, that’s why I require your help.

Thanks in advance!