[Support request] AquaValve5 – Not shutting off and completely emptying the Flexitank

I have 3 separate 15L (litre) autopot systems, all have the new aquavalve 5 and have been purchased brand new this year. All are also connected to flexitank pro’s.

12 x 15L autopots connected to a 225L flexitank pro. (Tomatoes)
6 x 15L autopots connected to a 100L flexitank pro. (Cucumbers)
11 x 15L autopots connected to a 100L flexitank pro. (mix of Peppers, chilli’s and melons)

All 3 systems have suffered an issue where the valve opens to fill the tray and does not close again, causing the tank to completely empty. Not sure why this is happening but I have now had to stand the trays on a 50cm saucer so I can immediately when this has happened and which module has caused the issue. The tanks are never more than just over half full as I expect them every week and change the water/feed solution. All systems are located within my polytunnel. All modules have the 6mm valve fitted (purchased from autopots directly),
so i can shut off any trays that are not in use. Happen once a about month ago and thought it was a one off. This has now happened 3 times in the last 10 days, no idea why. Especially as everything has been fine for the last month. Could do with some help/advise please.