I had a sneaky feeling that one of the old hands on here would have a solution. Thanks, HW3, much obliged.
@ Sailor Steve, I've had a few glitches with repeat starts of the same mission. The last one almost corrupted a nine patrol career when I tried multiple restarts with a different patrol grid and SH3 Commander took violent exception to it.
I've brought forward U-19's departure time to 0100 hours so they have a better chance of intercepting the convoy-to-be in deeper water and in darkness. It will also save on the flotilla's fuel bill.
KptLt. Zoff and his crew will be delighted that the 25 hours they have between arrival and departure will now be spent loading torpedoes, refuelling and provisioning the boat. I know they like to keep busy and there's nothing to do in WH when it's raining anyway. In compensation, I've promised them all extended leave when the war is over...