As all parametres seems right this case does look a bit odd
Especially as Len Poli´s 0,4% glucose (although I would use dextrose) dosage is one that I would use myself...
But I´m in no doubt that this is a case of fermentation running wild.
And it does require quite an (over)dosage of fermentable sugar to make T-SPX produce tangy sourness.
Mabye as you suggest the sweet vermuth toppled the fermentation proces by making the Pedioccocus as drunk as Danes (Here we say, drunk as a Swede

)
Jokes apart - it IS possible to make starter culture bacteria go beserk by adding some special potion - that is in fact how the "fast" starter cultures were invented
For alcohol in fermented sausage I´d rather stick to wine which usually have a low rest sugar content.
However, if the vermuth should have a sugar content around 10% them it only makes up for a total of 0,9% sugar together with the glycose.
Not really enough to turn the T-SPX into a acid monster. Some other unknown factors must have joined in
