You could well be right but it might be a part problem, have a look for the issue in the Mk3 as well as Mk4 Fabia forums and probably in other models made around the same time, I've seen this issue reported before but can't remember the outcome(s). You could see if there are any updates to the computer systems, often solving or patching over one issue to introduce two more. I forget, have you checked for an admitted Recall. - https://www.skoda-auto.com/services/recall-campaigns Silent recalls are a different matter, they are the ones they know about but don't want to advertise hoping customers will pay for the work instead, you need to find Technical sheets they keep hidden for those. I would still suggest you check the battery and as you have got an appropriate battery charger maintainer fully recharge the battery to 100% rather than the car's set of about 80% it will do a 15 month old battery good and if the battery is good at 15 months old hopefully it will take the charge well. Age of battery means only so much of course it's use (abuse and neglect) affects its performance and longevity, even a brand new battery potentially can be depleted for various reasons. Smart is only a marketing term, none of these things are smart, they are extremely dumb really only following rules, same for AI and "smart" phones and other devices. It is only recently I have been promoted to a "critical thinker" rather than a Luddite against technologies I and we were using and having problems with decades back. I totally agree and it is correct. They are to help (fiddle) the figures rather than help the engine. I proved to my neighbour that they don't even help with fuel economy as the systems can't (yet?) see the road conditions ahead and make the judgements the driver can (or should). It was and is all part of this. - SSP-426-Start-stop-system-2009.pdf As I put have a search I'm sure this thing has come up before but sorry I can't remember the results - and check and recharge the battery, checking it's charging on the car might (or might not) help but at least possibly rule it out. Good luck, let us know how you get on.