Nano 33 BLE starts in bootloader mode.

Dear Forummers,

I'm experiencing some weird stuff with the nano 33 BLE.
I have a circuit that has a L7805CV power regulator on it, this regulator goes into the vin pin of the nano.
When i put 12v on the regulator, it should start up and firing the uploaded sketch.
But Sometimes, it doesnt fire up the sketch, it's going to boot up in bootloader mode.
How can i solve this kind of problem?
I currently have like 30 pcs of the nano 33 ble family up and running, but with a battery failsafe system.
When the battery goes below 11V, it disconnects the nano 33 ble.
After disconnected the system, it recharges by using a solar panel.
If the battery is charged to 12,3V, it boot's up again.
But normally when the boot up is going to happen, the nano 33 BLE is going to fail, and starting up in bootloader mode.
If i manually reboot the system, the nano 33 BLE boots up normally.

I hope you guys have a solution for this kind of error, Best wishes Jeff.

No one has an answer on this one? thats new.

Best wishes.