SV'd does not fix everything. I do a lot of it , and in bulk as I like to work in batches.
I always aim for Sales , as i have a freezer full of the stuff ' just in case '
why should i pay more , and have to by a second or third freezer for my Hobby ?
one think I will not ever do is SV a MeatManagers almost the sell date special.
if Id get those , Id toss them of a very hot grill toot sweet.
which is not a decent answer to the OP.
most lamb in my area come in CryoVac bags. did you lamb that gave you pause come from the butcher's and was handled ?
if there is any question of your heath p SV just dump the bag
however you can learn from the Meats provenance for the future.
personally , if you are having to Boil-the-bag first to get good quality SV
and that's a recurrent problem
Id move to a different store and butcher.
and just to be very very plain :
did you wash your hands ? clean all surfaces and knives you used ?
repetitive hand washing in a Medical Setting or its lack probably cost us all
several billion dollars a year. maybe more.
just do it at home before SV