I have used ITZoo a few times for cheap second hand laptops, prices have increased over the past year due to increased demand but you can still get a good spec quite cheap from them with a legal version of Windows installed...there is also discount codes available occasionally so if lucky you can get even cheaper
As well as checking earth points, also check the 60amp fuse by the battery, it could be corroded or burnt....My brother had an issue recently with his TF so slightly different setup as there is a 80amp fuse on the back of the engine bay.
He'd changed the alternator around 18 months ago as his had failed for one I had in a boot when I bought a TF, this worked ok but sometimes the charge light come on. Recently he had issues where battery went flat (lockdown and dark days hadn't help) check with pscan all appeared ok but voltage showed around 11.9v, though alternator could be iffy, especially as it had come out of the boot of a car I bought so he bought another second hand one which had been tested and was ok.
Fitted it, check voltage using a multimeter was just over 12v which seemed odd, out of curiosity I tried to remove the 80amp fuse which refused to budge, even with a pair of long nose pliers it was still difficult to remove. Finally pulled it out to find half of one spade connector burnt away, swapped with new fuse and voltage went up over 14v.
In relation to the starter motor, I have an F and TF with an iffy wire going to the solenoid can be fine for months, then every now and again, I have no click on the starter when turning key and have to open boot to wiggle cable on solenoid. Usually this works but sometimes no amount of wiggling will get it to work when on my own. When this occurs I usually need someone to turn the key while I wiggle the cable...may get them both sorted one day but as it only does this now and again I usually just role my sleeve up and wiggle the wire.
Check the fuses under the dash...had my TF have the ABS light on recently, Pscan didn't pick up the fault, turned out the fuse was heavily corroded, as were a few other in the fuse box
Was using my Pscan unit earlier today and although having it since 2014 have only now noticed it has a number on the underside (000033). Just curious if this is a serial number of the numbers built?
Just programmed a spare (new) red fob I've got to a 06 plated TF PScan went through the motions said all programmed and works fine. Oddly, yet again with the barcode checker it comes up with *N24195AF6744B6AAE665FM* is NOT a valid Pektron barcode but it worked fine.
Cannot recall if the last digit matched, also; I only actually use the fob with one TF, I programmed it to two just to see if it would Oddly, just checked the bar code on the barcode checker would state it was a valid code and it says no...yet it programmed bar code was/is *N71BAAD5BDC7766B092C7M* is NOT a valid Pektron barcode.
I've bought two red fobs like that, first was from ebay, second one was from aliexpress....I've had no problem coding both fobs, infact, I coded one of the fobs to two different TF's I've got.