Immobilizer/Pektron Playing Up

I've had a bit of bizarre behavior from my 04 TF over the last week. Went to my garage on Friday unlocked and started up the car no problem. Left it to run for about 15 minutes while I sorted out some parts etc. When I came to lock the car up no response to the Pektron fob so locked the car with the key (had to close the passenger door lock manually). Back at home I changed the fob battery.

Went back to the car yesterday. Opened up with the the key (passenger door unlocked electronically). The clock had stopped or lost 50 minutes (on top of the change to BST). Started the car and drove 5 minutes to fill up with petrol. Didn't lock the car when going to pay. Come back and the car is completely dead, no dash lights, no starter. While sat blocking the pump contemplating how to push the car into the parking area and call the AA I had the brain wave that perhaps the battery isolator switch had come loose? It hadn't, but I turned off the battery then turned it on again producing a click from somewhere. All lights back car starts instantly. Back at my garage the fob locked the car as usual. Did this twice more as a test.

Does anyone have an explanation for this? Are these symptoms due to the battery getting low on charge? Does disconnecting/reconnecting the battery reset the alarm/immobilizer?

I had a similar sudden total lack of electrons that was fixed by disconnecting/reconnecting the battery with the isolator.
I took the isolator apart and found a small amount of corrosion/ build up on the brass was causing the issue. Cleaned it off and no further problems!

It doesn't take much grot to create a high enough resistance to drop the voltage to such a degree that the electronics fails to work. The resistance formed by little bit of oxide can strangle the current supply capacity for starter motors & other greedy devices.

Yeah you need to check the terminals for the furry green shit.