Intermittent dead battery - child lock fault?!

[Mrs_d]

Help!  We get intermittent dead batteries on our Skoda superb 2019. After three flats aa diagnosed faulty battery.  So we got a new battery.  Still getting intermittent dead battery a year, had  new aux water pump as it was drawing power even when off.  Still going flat - twice in a week and now the child lock fault showing on dashboard.  Battery has been tested and drop tested bit it’s fine.  No drains found - seems to be random.  However since the last few flats we now have child lock fault.  Could the fault be caused by the voltage drops as the battery has gone flat or could the child lock fault be causing flat battery?!   2 garages inc dealership and an auto elec and no one can find a drain.  
 

has anyone else come across this problem.  Getting desperAte as driving to Austria on dec and need superb to be reliable!