Panettone, lievito madre extremely acidic
Hello there, after trying to make panettone for a couple of weeks last year ( many tries resulted in it breaking apart when hung upside down) I ended up modifying the recipe a little bit by increasing the amount of flour and decreasing the butter in hopes for it to keep it's strength, and it was working pretty good, but recently I tried again and every attempt was breaking apart and it collapses as soon as I turn off the oven. After many thinking and troubleshooting I came to the probably obvious conclusion that it was the lievito madre.
The key differences this time is that I refreshed the starter in solid form for a week (before I would just make a liquid starter active and start 4 solid refreshments in water right away) on top of my internet router ( which probably is too hot?) and it even tastes and smells better than before after the final refreshment. But the first panettone dough rise it already smells pretty bad after 12 hours ( very acetic-lactic) and when doing refreshments to my solid starter it tastes more to the cheese side.
How is it possible that after doing so many refreshments suddenly the dough becomes that acidic and how can I prevent the lactic acid bacteria and/or others from taking over?
Also for this recipe I'm using margarine for the first dough and butter for the second(it wasn't a problem previously) but could it be another factor for the panettone dough being too weak?