Disconnect both front LED's
Consider disconnecting both front LED's. I do not know how a LED illuminates but it must be more complicated than a toaster element, basically what a filament bulb is.
A LED even when OK, inserted in the rear cluster can do strange things; but in the front and as supplemental signalling and when it is in good condition may not be seen by the monitoring systems. If however one of those LED's is defective, who knows what kind of signals it may be sending out.
You are making progress - yes probably the starting problem is related to the interlock - how one is supposed to figure out all these problems is beyond me.
Toyota had a similar problem that led to a recall of over two hundred thousand vehicles in the States - in this case, something about the brake light switch not telling the shift interlock it was OK for the engine to start.
Ten starts might have some affect on the battery.
When I was having my starting problems, every night I put my starting battery on the CTEK; also I have the Traxide system as well.
There is an argument for disconnecting the hot wire between the two batteries as the Traxide kind of kicks in and helps a weak starting battery and hence can mask a main battery problem. In your case, I do not think there is a main battery problem but there still could be a starter motor problem.
Ultimately my starting problem ended up being the solved by replacing the starter motor. I think the actual fault was with the starter solenoid rather than the motor portion. The distinction would be academic but I mention it as that was why the problem never showed what I call normal starter motor trouble characteristics - spinning of the Bendix etc or the click - well I did get the click now that I think of it but never when the battery was full up.
I also did not get any HDC messages - well I did on occasion until I replaced the brake light switch. I always use OEM bulbs - always did so in my Chev's and the like previously as aftermarket bulbs are to me, always in question.
I think you are getting close to resolving the problem.